2060 Mhash/sec @ 498 watts -- 4.13Mhash/watt (918 mV, 900Mhz/160Mhz) (all cards stable)
If you still think these cards aren't efficient, you're drunk.
Fascinating! That's with 4x 7970?
3x 7970
Mining: 925/150mhz, 865mv, 354 watts + 270 idle = 624W.
~1650mh/s
Even with similar clocking, you are pulling 50% better efficiency than the OP! You added an entire extra card, and dropped more than 100 watts. How???
160W lower idle. Replace heavily overvolted OCed PhenomII with undervolted AthlonII or Sempron and you're mostly there.