Xeon 3250 2.6 @ 4GHz running stable under 70C. I put a 110CFM Slipstream in for exhaust and with the fan speed controller on about 1/3, it's optimally quiet as well as getting plenty of air.
http://c4.ac-images.myspacecdn.com/images02/135/l_0b82c78f472b479d986517d56fcf044b.jpg...
You can probably tell by the pics that we're already pretty good at that (I've done about 30 mini's now). Btw, in the liquid one, that's a full 650w Seasonic with all it's full-length cables - that's not easy to hide ;)
The temperature I was using was on the case and is incorrect (it was correct at lower temperature ranges 30-44) - I hit about 59ºC under load according to the Gigabyte utility. I'm going to edit my original post to correct that :confused:
Update: I'm 55º stable in Prime95 @ 3.3GHz & 1.45v...
Q6600 Kentsfield 2.4GHz @ 3.4GHz @ 1.5v @ 59ºC under load on a Gigabyte G33M-DS2R Motherboard (Bios is F4a beta to get the 1:1 divider), 4GB DDR2-800, 8800GTS 640MB Vid. Seasonic 650W PSU