I'm presently running an Nvidia 6800 vanilla with 128mb on an AMD 3700+ and 1 1/2 gigs of ram. When running FSX the system runs OK but slows to a crawl while it is getting new textures. I've been looking at an Nvidia 7600GS with 512mb. Would this be a better upgrade than, say a faster 7600GT with only 256mb? I guess what I'm asking is...does FSX take good advantage of the video ram over 256mb.

A lot of people with 512mb cards say it does better. The only problem is they are talking the ATI 1900 and Nvidia 7900 series of cards mostly.I would wait another 3 weeks and see what nvidia has in DX-10 also that should drop card prices down even if you still want to go with the DX-9 cards.