Lol. I'm running same thing as you. B3 on P5K Deluxe.
Stock cooling is DEATH. I have to have the fan cranked at 100% just to idle at 45C . Load at 51-55C (depends how hard 8800's fan is on. At 85% Load temps = 51)
If I put stock fan speeds below 50 itll Idle in the 65C mark. Load will push over 70 sooo I just leave it 100. This is stock speeds XD Case has great airflow. Like a little wind tunnel in there. It's just throwing off a lot of heat. More than I expected actually lol.
If you ditch you stock cooler you should be able to get 3.0 on Air without many troubles if you keep the fans running at a decent speed.
I'd post some OC temps but I've got to RMA the p5k cause of problems. Meh. I'll be droppin the q6600soon as I can lol.