Lord Gornak said:
Why would you put racing stripes and spinning rims on a primer gray 1986 Ford Aerostar? Cause it's cool!
HAHAHA! YEAH I HAVE 1GB of video memory man! My monitor is an ol 15" 800x600 4" thick LCD from 2000 though. But it has Stripes.
To the OP, The obvious choice is keep the 8800GTS 320M. Depending on what res you are looking to play at the GTS will last you till the end of the year maybe. The 8500GT is NOT a gaming card at all. the 8600's are sort not gaming cards but more multimedia cards that can pull off some games, but deffinitly not an 8500.
COD4 scales EXTREMELY well. You won't be able to max out on certain resolutions but you should be able to turn up some of the warm fuzzies. My x1900xtx played at 1680x1050 with most things on mediumish settings, and your's should slightly outperform that. Oblivion will be mediumish as well.