I have a Q6600 and 8800GTX in an Asus P5E X38 mobo, loving it, upgrading again soon though to something with sli, dont know what yet but hey, may go skulltrail, depends on if I want to spend £1,000,000,000's on something I dont really need.
As for stable overclocking, I have mine a 3.8ghz stable, 24/7 on 1.54vcore fully watercooled.