3x 3gb (if i get 3 580s) of ram = 9gb total i can use
4x 2gb (if i were to get 4 6970's) of ram= 8gb total i can use
the point of this thread was to see what would be the best option for the most amount of ram because i am working in large resolutions!!!!!!!!!!!
and for those who posted "oh this is not a fair competion" well 4x 580 with 512mb of ram each equal 4gb or ram total, and 2 6970 2gb each equals 4gb total
GTX580 has 1536 mb - doesnt matter how many more you add, you will only have 1536 to work with.
6970 have 2gb - so matter how many more you add, you are using 2 gigs.