Oh, I know it's part of the spec - but the Nano doesn't go above the backplate, so they'd look even better in a volume-based comparison. I'm going to retract my call for fps/cm
3 though - in keeping with the fps/inch concept it should clearly be fps/fl. oz.!
EDIT:
AFAIK it's very hard to dissipate more than ~ 100W with a single slot cooler, and even then you're on the ragged edge of what's possible. AMD found that out when they tried a single slot 4850 and got hammered for it running hot and being very loud. And fo course, by the time we get current high end performance in a sub-100W thermal envelope, it won't be high performance any more!
The only way to effectively cool a high end card in a single slot is with a custom water block - but then you're looking for somewhere to house a pump, rad and fans too. So no, there won't be any high performance single slot cards suitable for small factor PCs released soon.