The case for FPGA boards as I understand it:

ATI 5850 can give about 400 MHashes and uses about 200 watts. (ie at best 2MHashes/watt)

Dual FPGA X6500 gives about 200MHashes and uses 20 watts. (ie. at best 10MHashes/watt)

If we were to keep 2 rigs, and sell the other 11 at... $450? each. That'd give us $4950 which buys us 9 Dual FPGA X6500. So we would go from...and I'm really speculating here, assuming quad 5850's on 13 machines...
4x400x13=20800MHashes peak output

To 2rigs+FPGAS giving (4x400x2)+(9x200)=5000MHashes peak output.

In terms of power, I believe Tawsix quoted about 700 Watts per rig. So we would go from 700x13=9100Watts to (2x700)+(9x20)=1580 Watts.

Long story short we would have a drop of about 75% in btc generated. Our efficency per wat would go from 2.3MHashes/watt to 3.2 MHases/watt. Thats almost a 40% increase in efficiency.

My brain is too tired to turn that into dollars. And I may be making a million basic mistakes in my calcs, feel free to correct me. Long story short, I guess we might become profitable again, but the amount of bitcoins we would generate would be tiny. Tiny amount of bitcoins, and weak bitcoin values, means very little return on investment. To me, liquidation still seems a better option.

/discuss

Esteban Prieto