6870 (only 2 way compatable) not an option any longer
a 6950 2gb for $200-220
a 580 3gb for $610-650
so roughly around same price.
which would get he best fps at say 3000 x 1000 resolution.
The tri 6970s would sometimes dramatically improve performance over 1 of them, and sometimes even lower performance, so I suggest you go with the 580 for more stable performance.
oh, really? yea but the 6xxx series scales very well and you can get up to %200 on two cards. which would be much better than a single higher end card. but really i just want the best performance. and for rendering blender and 3d rendering programs.