seriously mate, an 8800 GTS will CLOBBER UT2K7. Really an 8800 GTS is SERIOUSLY SERIOUSLY SERIOUSLY, sickeningly fast.
I you go up to 2GB of RAM, and whack an 8800 GTS in, your system will easily be ready for Crysis, let alone UT2K7
I find these forums so funny. So many people here seem to be under the impression that a 640MB, 1500 MHz, 500 MHz, Direct X 10 capable card, with a unified shader architecture and many other new tricks is merely a "stop gap" card, which will last them till the end of the year...
The fact is, there is NOTHING currently out that will even make the 8800 GTS even break out into a sweat, let alone shrivel and die.
I fully expect that, paired with a decent CPU and RAM, an 8800 GTS will be able to max out Crysis....