cscape reported getting 40GH/s @ 35W is there any demonstration of it being pushed higher?
If you don't have the budget for a large number of chips, overclocking is the best option, as it will get you 40GH/sec out of a card (probably more with better cooling), instead of 25GH for a standard H-CARD for the same 16 chips. At 40GH/sec, the card uses about 35 Watts, running off a standard 12V DC supply.