I wouldn't recommend the Asus P5B Deluxe. Mine will not go over 300Mhz with either an E4500 or a recently purchased Q6600. I have tried two different memory manufacturers PC2 6400 Cas 4 DRAM (seperately), but the result was the same.
This and
this, yet nothing over 300. I've tried another power supply and unplugged the other HD and the DVD (in case 500 watts wasn't enough), results the same. No SLI, just one video card.
For about 9 months I had the ratios with the memory twisted such that the memory was running at 450 (3:2 with the bus at 300 IIRC), never had a problem. I doubt it was bum memory.
There was a well composed OC guide arround here which the author used a P5B and the author apparently had an easy time of it. I followed the same guidelines, my board will not boot over 300Mhz.
Good luck.