This is my speculation. The p5k has 6-phase power (I cant see any specs yet but just guess by counting the chips where half are cooled). The p5k deluxe has 8-phase and is written this way in the specs if u google it. The gigabyte p35 dq6 ( & p965 dq6 incidentally) have 12-phase power. Also a bit of folklore is that quads require even more stable cpu voltage regulation than 6-phase allows.

My conclusion is that a 6-phase p35 would have questionable overclocking results with quad cores. Thats my opinion until proven otherwise.