2x 6950 2Gb's should handle that easily,
Stolen from
http/www.amd.com/us/products/desktop/graphics/amd-radeon-hd-6000/hd-6950/Pages/amd-radeon-hd-6950-overview.aspx#2
under the specifications tab.
■AMD CrossFireX™ multi-GPU technology6
◦Dual, triple or quad-GPU scaling
■Cutting-edge integrated display support
◦DisplayPort 1.2
•Max resolution: 2560x1600 per display
•Multi-Stream Transport
•21.6 Gbps bandwidth
•High bit-rate audio
◦HDMI 1.4a with Stereoscopic 3D Frame Packing Format, Deep Color, xvYCC wide gamut support, and high bit-rate audio
•Max resolution: 1920x1200
◦Dual-link DVI with HDCP
•Max resolution: 2560x1600
◦VGA
•Max resolution: 2048x1536
The reason I ask about your cooling is that crossfire/ SLI'd cards can suffer, especially the top card in the set up, if your watercooling its not an issue but with air its vital you are on the ball to avoid cooking the cards, the gt's sidefan better be up to it lol
I assume your looking for dual slot editions, not the triple slot?,
You must be there aren't enough pci slots for three triple cards
and different cards can have differrent pcb's, a lot of them the bios switch lets you flash the cards on a secondary bios chip, if it goes wrong then you have your 'backup' bios (which cannot be flashed)
on my Asus 6950's though, that switch is used to alter a display port/dvi function,
So options really at this point are,
research different manf's cards and decide which you want,
decide if you still need or just want trifire instead of crossfire with two cards
and possibly think about watercooling the cards, if not the Processor,
If you do have three cards in there I strongly recommend that as your cooling
Moto