Had the same temptation.

Assembled a rig:

H81 MB, 6 ea ASUS Stryx R9 380 4GB cards. About 185 Mh/s @ 900W (Kill-a-Watt P3).

For 900W, cclock 800, mem clock 1500.

This card has I believe a somewhat larger cooler for running warmer and quieter.

I don't recall that this card's bios could be modded.