they are releasing another 8800GTS with half the ram (320 MB) for as much as $100 cheaper than the original. R600's come out in a few weeks as well.
Wait until Crysis or a DX10 game is even out though before you buy a DX10 card, there is no use in building it now until you know what you need to run it. If Crysis comes out in August, then buy a DX10 card in september and see if your current cpu/monitor/ram setup can handle it with only a GTS...or maybe you need two etc... Maybe DX10 is actually FASTER than DX9...no one knows yet, so just keep an eye out and build when you we know more about such things.
3DMARK VANTAGE: 11,500
GPU: MSI GTX 260 @ 650MHz/1175MHz
CPU: Intel E6750 @ 3.4GHz/1.33v/60c
HSF: Arctic Cooling Freezer 7 Pro
MOBO: MSI P6N SLI-FI 650i
RAM: G.SKILL 3x1GB DDR2 800
SND: Creative Audigy 4
MOS: Logitech MX600 Wireless Laser
LCD: HANNS-G 28" Widescreen