Couldn't tell you, my rack just filled up over double digits now XD

But yeah, still though an 8 core mid 3ghz Xeon with some 2666 or higher is pretty useful. I'm at ~50 watts on those units. Which is pretty good I think. That said, I think those who are willing to put a laptop in the closet aren't using modern hardware. That and unless you're talking about a gaming laptop or an "ultrabook" or whatever the kids call them these days, I don't think the hardware can compare in actual workloads with high duty cycle on 5+ yr/old gear.

Even still the r340 series have come down dramatically in price, so your talking 5 year old equipment, possibly still cheaper than a laptop with similar processor and memory throughput.