I would buy MSI Big Bang-Marshal. Yesterday there were two of these on Amazon for 360 CDN a piece. Then fill all eight slots with these slim bitches:http://www.techpowerup.com/179080/Colorful-Announces-iGame-GeForce-GTX-650-Ti-Single-Slot-Graphics-Card.html. Equip it, I would, with some 2-cores, 4-threads processor(pick one, my personal favorite is i3-3220 or i3-3225) and thats it.
If deviation from average price of 650Ti is not that big, then 8 of these cards would cost like single GTX 690 or somewhere there. Such system would produce 100K+ RAC(mostly like 120K) a day, for 550-600W total power consumption.
Of course, there are other choices of motherboard. PCIe x1 slots can be modified to accept x16 video cards(made it for bitcoin miner machine) on some cheap boards, no matter what brand and platform it is. Most important, now there are most energy effective cards in single slot variant available(or available soon I hope).
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I would buy MSI Big Bang-Marshal. Yesterday there were two of these on Amazon for 360 CDN a piece. Then fill all eight slots with these slim bitches:http://www.techpowerup.com/179080/Colorful-Announces-iGame-GeForce-GTX-650-Ti-Single-Slot-Graphics-Card.html. Equip it, I would, with some 2-cores, 4-threads processor(pick one, my personal favorite is i3-3220 or i3-3225) and thats it.
If deviation from average price of 650Ti is not that big, then 8 of these cards would cost like single GTX 690 or somewhere there. Such system would produce 100K+ RAC(mostly like 120K) a day, for 550-600W total power consumption.
Of course, there are other choices of motherboard. PCIe x1 slots can be modified to accept x16 video cards(made it for bitcoin miner machine) on some cheap boards, no matter what brand and platform it is. Most important, now there are most energy effective cards in single slot variant available(or available soon I hope).

Did you ever try to set up a pc with 8 vga?
It is very VERY difficult.
Once upon a time here at the office we setup a machine with seven GTX 285 for rendering purposes ( not SETI ) but it was extremely difficult. There where blue screens, no boots,
driver limitations at that time etc.

Yes, I know I might expect problems, but I won't hesitate even a second to try to build it :) It 8 GPUs, Win7 supports 8, there are machines running SETI with same number of GPUs, even you have one I see.
I myself had machine with 4 GT240s. There were problems too, but adding cards one by one did the trick.
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Yes, I know I might expect problems, but I won't hesitate even a second to try to build it :) It 8 GPUs, Win7 supports 8, there are machines running SETI with same number of GPUs, even you have one I see.
I myself had machine with 4 GT240s. There were problems too, but adding cards one by one did the trick.

Be aware…

It is not the same thing.
The difficulty is to add 8 vgas, and not 4 dual gpu cards like 295, 590, 690.