Here is what I would do for $1500.00
For $1800 throw in a 19" CRT & a Audigy 2 ZS OEM Sound Card
AMD Athlon 64 3200+ Venice - $190
DFI LANPARTY UT nF4 Ultra-D - $129
ZALMAN CNPS7000B-Cu LED - $50
eVGA Geforce 7800GTX - $519
OCZ EL Platinum Revision 2 1GB (2 x 512MB) - $170
Seagate Barracuda 250GIG SATA - $111
Thermaltake Tsunami Case - $100
PC Power & Cooling 510w Turbo Cool - $219
That's roughly $1520 USD with S&H - There are also about $37 In rebates from newegg.
As long as you have the other components like you said you did, this Build will be MORE then enough for you to play all current games on high settings....