GTX 470 sli , As you don't care about the cost get 2 GTX480 !!
5970 is very expensive , out performed by 2 GTX 460 , So imagine 2 GTX 470 ,
GTX 470 sli will support 3d vision , 3d vision surround , physics , cuda and better performance , there is no comparison man , they are also cheaper than 5970 .