If your goal is to get a massive e-cock from your texture memory just make sure you get a card thats actually fast enough to allocate that much memory, i've seen 512mb 6800s perform the same as 128 mb 6600gts... I wouldnt outright go for SLI off the bat, thats more of an upgrade thing. Wait for a game to be released that actually stresses a 7900. Instead of spending an extra $300 or whatnot buy 3 250 gig seagate SATA drives and run raid, i cant remember the type off hand but the one that gives you double redunancy + extra performance and only costs the space of 1 drive.
I would NEVER buy top of the line cpu, there is ALWAYS a curve where you lose out on value if you go too high end, you'll end up..... Actually looking at newegg this isnt quite the case as much as it was in the past, i seem to remember those stupid fx 55s and shit being 4x more expensive than slightly slower cpus. Regardless i doubt the performance difference between a 4200+($357) and a 4800+($632) is anywhere FUCKING CLOSE to being worth spending nearly twice as much, this again is something that should only be purchased for bragging rights as a 4200+ is a VERY fast cpu. Again here you could save nearly $300 that could be used for another video card, better drives, or something else that would be more usefull.
Benchmarks to back up the very small actual difference in performance: http://www.anandtech.com/cpuchipsets...i=2410&p=4
5-10% difference for twice the price is a baaaaddddddddddd choice, i cant see why people would suggest something like that.
Two gigs of ram atleast, i dont think xp even uses over 3 gigs, but i know xp 64, server 2003 do and so will vista. Personally i wouldnt even buy an expensive video card if you plan on getting vista when it comes out, as only dx10 cards will be supported(of which there are none currently).
In conclusion: LOOK FOR VALUE, NOT BRAGGING RIGHTS! =D Nobody cares how big your e-cock is if you overpaid for all your shit.