ghostwes,
Well, I started buying parts for the desktop almost a year ago, so some of my choices don't make sense in the current market. It was put together for me by a young fellow gamer who has the degree and makes his living at this (ex-Geeks-On-Call) but there were many demands on his time (read: delays to my PC) through the spring and early summer.
I got an AMD X2 4000+, w/ the 1 Mb cache for a big discount, just as they were revamping their line (and before the Intel Core Duo hit the streets like gangbusters). It was the best deal I could see that put me into the AMD AM2 socket architechture, which should be upgradable without a MB change to AMDs 1st gen true quad procs when they come out early next year.
For those on-the-horizon upgrade considerations, I got a top flight full featured MB from Gigabyte. It was Max PCs top rated AMD board at the time. I think choosing a forward looking mobo and socket is always your most key choice in a new custom-built PC.
I was shooting for the quiestest 'pretty-darned-good-performance' PC I could pull together for reasonable dollars (ended up something like $1250), so after spending some time reading articles on www.SilentPCReview.com (a good source for general perf info on adjunct parts in general, too), I got an Antec P180 quiet case, a WD Raptor 150Gb as an OS, swap, etc drive, and a WD 7200rpm 500Gb as main storage. 2 Gb of DDR2 Corsair 800mhz Dominator memory seemed to be the price-performance sweet spot from my then current (last fall+) reading. (Faster and lower latency give measurable but marginal improved performance probably not that important for games 'n stuff I do, but at big price premiums; the Dominator extra cooling contribs to an overal cooler, quieter machine, though.) Got a pair of Nvidia 6800s from a friend who was buying an 8800 GTX; they run hot counter to the general theme of this box, but they a) were REAL cheap,

in SLI they'll run everything I was interested playing currently (Oblivion was the benchmark target; my PC builder tested with Supreme Commander with pleasing results), c) the rest of the box runs so cool n' quiet we could afford the extra heat. Though I looked into CPU coolers, with the relatively low-end CPU from a relatively cool line, I decided the stock cooler was fine; we weren't overclocking. AMDs stock cooler is pretty well rated for temp and noise, anyway.
I was gonna go with the 4-year old Plextor DVD from my old machine that fried (ahem-warning to all AMD T-bird series owners; great chips but if your cooling gets the least bit uncertain, watch out - internally they can get very hot...briefly); I don't burn much, and after all does it really matter if you load a game in 2 minutes vs 1 minute. However, while Michael was still building, the DVD on my second PC (my young son's, a recent but bottom of the line Dell) crapped out. I won't say I suspect mistreatment, but some of the CDs that go in there have been found to have fingerprints in a jelly-like substance (grape, I think.) So I scored a Plextor 755SA SATA drive for the new PC, again just before they discontinued the item, and put the recoverd one in the junior workhorse.
I still had my MS Natural keyboard, Logitech gaming mice, etc. I had not long before purchased separately a Dell 2405 24" widescreen LCD monitor (to DIE for!). Note that the Wide 24" format is a particular sweet spot because the native resolution is 1920x1200 - that means that if you are letter-boxing games, etc that don't do widescreen, you can get a natural 1600x1200 pixels. Thats also a way to run more demanding stuff with more features turned on, just set the card and monitor for the 3x4 ratio.
If I was selecting the components for a similar rig now, I'd have to make it an Intel box, probably a 6600 proc from the casual reading I've been doing. And I think the case for NV 8600/lower end 8800 v-cards is pretty compelling. I think my choices for other components would still be about the same. In particular, 4 Mb and high speed and low latency RAM still seems to be overkill.
I recently also ordered (not delivered yet) a Dell laptop. I like Dell's for ordinary stuff, and for configs you aren't going to mess with, like laptops, but you have to work their on-line coupons and watch their on-site discounts very carefully for a few weeks to get the best deal. Don't order any of their unnessary support plans, and work their configurator very carefully for the machine that just meets your needs. Generally that means starting with one of their low or mid-range offerings and adding just the plus-ups you want. If you start with one of their higher range baselines, you may find that some components that you want to economize on don't step down to the more modest parts available as
upgrades on the mid-range configurator.
I used to really like ABS computers (www.abspc.com, I think). Still do, but in recent years they have become much more of a niche high performance, higher price-tag shop. You can still get a cutting edge rig from them for cheaper than VooDoo or Falcon or Alienware, however.
well, that about drains my expertise. I'm not actually an electron-herder myself, I just tend to do a lot of wide ranging reading when new machine time approaches, and I know some good sources.
drrider