I've just put an EK fullcoverblock (nickel/acetal) on both my 5870's and temps are fantastic! One card idles at 27ºC, the other one at 29ºC. A full run of 3d mark 06 only heats them up to 31-32ºC! VRM temps are also very good.

I was able to do 3d mark06 at 1020MHz w/1.237V. Me happy? H3ll yeah!