I like (and agree with) the suggestion of the new Pentium CPU, BUT! it's going to cost around $1100 for the CPU (plus a brand new mobo (new tech) so that is expensive, and really good cooling (unless you want it to idle @ 65C and load at just under 80) and a huge PSU
so i'd not do that on a $2000 budget (on a $3000 budget i'd do it)
SO
my suggestion is to buy an Athlon64, as it's going to handle your gaming needs
you don't need an FX series chip, as the high end desktop series will suit you (also, DO NOT buy the Cyberpower system, for $1900 it's a rip off)
I would suggest an Athlon64 3500+, 3800+ or 4000+ (i'd suggest the 3700+, but it's Socket 754 (no PCIE for that socket, so it'd be stuck to a single graphics card)
So an Athlon64 3800+ is probably the best blend of prce and performance (around $400, the 4000+ is nearly $600, and the 3800+ is about 10% slower)
for the motherboard, I WOULD NOT BUY THE ASUS, get the DFI LanParty nF4 SLI-DR or DFI LanParty UT nF4 SLI-DR (the UT is cheaper, but not sure which features it loses to be cheaper)
as to the graphics, I would select 2 GeForce 6800's as the cost is managable ($400 CPU, $220 mobo, 2x$325 gfx card...it's gettin up there)
next to that you'll need a hard drive (Newegg has a 250GB SATA drive for $131 right now (i'd grab it)
WindowsXP Home or Pro (your choice, Pro only adds greater networking features, if it were me, i'd buy XP Home)
and then a sound card
I suggest the Creative Labs Audigy 2 ZS Gamer Edition (the Gamer Edition is an Audigy2 ZS but includes 5 games (some of which still cost $20+, so it's just a decent deal imo)
you can always step down on the CPU (what i'd do) and get better gfx (it'd actually give you more power, no joke, dual 6800U's or 6800GT's with a 3200+ vs dual 6800's or 6600GT's with a 3800+, the 3200 system would win)