The thing that is bogging down your PC is not your video ram its your system ram. When I started I was playing on 512mb system ram and a 64mb geforce 3 :( Yes the original Geforce 3. Not even a TI anything, just to give you and idea how old this thing is. Even at extreme performance, the game was practically unplayable in town unless I rebooted every other time I zoned. Upgrading to 1.25gb of Ram I no longer have to reboot at all, but because of the crappy video card I still can't move beyond extreme performance or my fps nosedives.
Fortunately, I will be upgrading to at least a stock 6800 as soon as I find a reasonably good deal, like the compusa one I missed a couple weeks back. Till then its more sucky graphics for me.