8800GTS 640 or 320MB for 1280x1024 gaming

Alright so i currently use a 1280x1024 monitor but intend to upgrade to a 1680x1050 before next summer. My question is, should i go with the 320Mb version of the 8800GTS over the 640Mb version considering my relatively low res? Also, is there a big difference between the two at higher resolutions like 1680x1050. Since there is a 110$ difference between them, i think i would go for the 320Mb... unless there is a major imporvement with the 640Mb. Thanks in advance

I think the 640MB version would be better even at 1280x1024.

Games like Quake 4 already use 512MB GFX if you want "ultra textures". So in the long run more RAMs would probably be beneficial.