Well, either my P5WD2-E or my 920 is not too happy with the cold, but it does a bit better in the Mach II GT:
Max speed, so far is a 5116 Mhz http://valid.x86-secret.com/show_oc.php?id=70240
3dmarks run @ 4906 Mhz: 3dmark2001se 40886: http://service.futuremark.com/compare?2k1=8894960
3dmark05 12639: http://service.futuremark.com/compare?3dm05=1792634
I haven't tried PCMark at anything higher than 4766 Mhz yet, but here's a 8203 score at 4766 Mhz: http://service.futuremark.com/compare?pcm05=268396