I just returned an eVGA geforce 7300 turbo cache card for a dedicated geforce 6600 256mb card after reading about the technology (also, i dont have much ram to spare)

Id advice to stay away from the Turbo Cache technology, however, you seem to have more than enough ram to share. But remember that you will get minus 192 MB of your regular ram available because it will be wraped up in video. The card will recognize that there is 256 MB avaiable but having dedicated memory on the video card itself is a better way to do it. Also make sure you get PCI - Express and not AGP type. PCI Express way faster.

I personally would rather have a higher end 6 series (like a 6600/6800 GT) than a lower end 7 series w/ turbo cache)

It should keep up with BF 2 and current generation FPS games though, so your call.