As promised, today I thought I'd finally getting around to writing a buyer's guide of sorts. Are you envious of people with high-end uber-systems? Do you wish you could buy a PC that gives you high-end performance, but you don't have unusually high amounts of disposable income? Well then this guide is for you. I'm going to show you how you can build a system that really rocks without paying through the nose.
Now most buyers' guides have parts included, and I will show you what, as of the time of this writing, I believe to be the best value. However, since the PC market changes so quickly, I also want to impart some common-sense lessons that will be applicable in the future as well.
So without further ado, here's how to do it.
Base System Platform
The Base System Platform is the motherboard, processor and memory. It's also where most people go wrong. The wrong decisions can cost you hundreds of dollars in useless features and non-existent performance increases.
The Motherboard
When buying a motherboard, ask yourself the obvious: what do I need? The nVidia 680i is an awesome board – it overclocks great, has three "true" PCI-E x16 slots (meaning that they stay x16 slots with multiple cards). So the question is... do you need that? First of all, consider the disadvantages of SLI – inconsistent performance, no triple buffering, and extreme cost. For our system, we'll be wisely sticking with a single-card setup. So screw three PCI-E slots. Who the hell needs that?
The nVidia 650i is a ridiculously good value: It costs just $150, nearly $100 less than the 680i; it features 16x bandwidth (on a single card setup; SLI is reduced to 8x) and it can hit 500mhz FSB no problem, just like the 680i. That's all the power you need for overclocking your processor without wasting money on features you don't need.
Now, say for the sake of argument that you might be entertaining the idea of eventually going SLI. First of all, you shouldn't. I've done it and it's not as good as people assume it will be. But if you do, consider this: there is zero real-world performance difference between 8x PCI-E and and 16x PCI-E. Think about that when PCI-I 2.0 comes around. Don't believe the hype, kids.
On the downside, this board only allows for "only" four SATA Hard Drives. If you plan on using more than four hard drives, in which case you really don't have "value" in mind, buy the more expensive version of the 650i, which rings in at around $200 and allows six Hard Drives.
Motherboard pick: ASUS P5N-E SLI LGA 775 NVIDIA nForce 650i SLI ATX Intel

Processor
Gaming is not bottlenecked by the processor in all but the most extreme cases. [H]ard OCP found a very small bottleneck with two 8800GTX cards in SLI. Even with that being the case, current Intel processors overclock like crazy. Don't waste money on a 2.9ghz x6800 ($970); it's not uncommon for a lowly E6300 ($180) to clock well past 3.0ghz. I've seen reports of clocks as high as 3.5ghz on the 1.8ghz E6300. That's all the processing power you will need for quite some time. Some alert readers may note that the E6300 features half the L2 cache of some of the pricier Core 2 Duos. The extra L2 cache may increase performance slightly in some office applications. Is that what you're spending money for? You want frame rates, dude! The E6300 is an insane value thanks to its obscene overclockability.
Processor pick: Intel Core 2 Duo E6300

CPU Cooling
Fact is, you can't get optimal overclocks on stock cooling. But who says you need water cooling or some other exotic solution? OverdrivePC, who overclocks their chips very far, uses humble factory copper coolers.
For low noise and great cooling, you can't go wrong with Zalman, so I recommend their CNPS9500, which is under $50. You can get the larger 9700 version, but it may not fit in your case and it will only make a minor difference over the 9500.

Memory
Memory is perhaps the single most overrated aspect of PC performance. There's just no reason to waste money on super-fast memory. Latencies do affect frame rates somewhat (though only slightly), so I do suggest getting quality memory and not Corsair Value or something like that. But do not blow your cash on pricey memory.
G.Skill is fast becoming popular among gamers for making top notch memory that doesn't cost a bundle. To go with our 650i motherboard which uses DDR2-800 standard, we'll use G.Skill's PC2 6400, which dials in at impressive latencies of 4-4-4-12 and costs a mere $200 for 2GB. Similar performance from Corsair or Crucial can easily exceed $300.

Hard Drive
You've probably seen and drooled over the Western Digital Raptor high-speed hard drives. Falcon Northwest and Voodoo commonly stick two 150GB Raptors in RAID 0 for super-fast drive speed. However, consider for a moment the value. With high-speed drives, your load times will be reduced and applications will load faster. The question here is simply whether this is worth the cash for you. In my experience, load times on a 7200rpm drive are barely worth mentioning. A 320GB Seagate 7200rpm drive costs around $90. A 150GB Raptor costs around $225. Is the premium worth it? Well, for a kick-ass PC with the best possible value, hell no it's not.
Hard Drive Pick:
Seagate Barracuda 320GB 7200 RPM drive

Disk Drive
This one's easy. Screw the Plextor drives that cost over $100. Panasonic makes great 18x DVD+-R/W drives that feature Lightscribe technology (label making) for around $30.

Graphics card
Yes, the 8800GTX is awesome. It's insane. And Big. But you know what? If you overclock an 8800GTS, you can get about the same performance as a stock 8800GTX for roughly $150-$200 less. And you don't need as big a power supply, meaning you save even more money.
And don't even think about SLI. It's expensive, performance is unreliable, and you lose the ability to use triple buffering programs like Direct3D Overrider – meaning you get either V-Sync or great frame rates, but not both. Also, a single GTX-level card will easily play any current game at better-than-max settings. As I mentioned in the previous post, I'm playing all my games with 8xQAA, 16xAF and High Quality Texture Filtering with an overclocked 8800GTS. And that includes Oblivion.
Graphics card pick: nVidia 8800GTS and a download of Rivatuner 2.0 (free).

Power Supply
Yes, 1000w PSUs are all the rage. Why? Because savvy marketers have convinced gamers that they need them. Would you believe that an 8800GTX SLI system with an overclocked quad-core QX6700 can run just fine on a 500w supply? It's been done. Not that I'd necessarily recommend running on a such a slim margin of error. But for this system, a 600w will be plenty.
OCZ makes some of the best PSUs around, which is why I recommend their GameXStream 600w PSU.

The Case
Okay, so what should we stick this whole thing in? We want quality, but not super-expensive quality. Again, don't pay for features that you don't need. Are you going to use 6 DVD drives? Then why are you getting a case with 6 or 8 or 20 drive bays? Are you going to use more than four hard drives? No? Then you do not need a full-tower case. Stick with a mid-tower.
There is no better manufacturer of mid towers than Lian-Li. I use their PC-6070 Plus II, which has been used by Overdrive PC and Maingear to name a couple of boutiques. It's still a great case – brushed aluminum chassis, great temperatures, easy access, thumbscrews, plenty of room (even for an 8800GTX), four 5" drive bays and three 3.5" bays, and sound-insulating foam on the interior making it one of the more quiet cases around. At just $130, it's a far better value than the full-towers that often push $300 and are chock full of useless features and excessive space. And I still love its sleek, curved, classy look.

Total Cost for this system = $1,381.92
If you were to buy a system with this level of performance from, say, Falcon Northwest, you'd pay for a much pricier case, a motherboard filled with features you'd never use, more expensive memory, an excessively powerful PSU, uselessly fast memory, and of course labor and a brand name. I configured a nearly identical system at Falcon NW's site, and it cost over $3,000! That's more than double the price, and with a little overclocking your system will be much faster than Falcon's.
In the end, if you play it smart and buy what you need instead of what sounds cool, and you use overclocking to create a tremendous value for midrange parts, you can build an amazing system without breaking the bank.