in general, 7800GT or 8600 GTS Or 2600 pro?

i currently have geforce 7800 GT 256MB. bioshock framerate isn't all that good in 1280 on 720 on high detail and lowering graphic detail isn't something i want.

would getting 8600 GTS or 2600 XT or PRO improve this? no review i saw compared those to 7800GT, also, i don't care for dx10 right now.

http://www.amdzone.com/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=315&page=1

8600gts would be a slight improvement like the other dude said get an 8800