I personally use these on my fpga rigs - one of these 1000 watt babies will easily power 8-10 54Gh/s bASICS
There you have it guys, thats the power estimation, now we know its NOT "up to 10 27GH bASIC" devices.
So, power consumption is anywhere between 1.85w/GH to 2.31w/GH
It could be lower than 1.85J/GH (or W/(GH/s), but you get my meaning). Tom said "easily power 8-10 54GH/s bASICS".
If it's easy to power 8-10 it should be easy to power 10. I suspect this fuzzy estimation is because he knows the absolute worst case scenario for power requirements and it probably involves bASICS running at more than 54Gh/s (through better mining software or overclocking) in this worst case 8 should be the max. But in a more likely configuration (no or small speedup) 10 should have a healthy margin : <1.85J/GH.