I have found the 0504 bios quicker than 0612 for me....I am using OCZ ReaperX 4gb kit (2 x 2GB) at 1066 2T 5-5-4-15-3-46-4-3-3 @ 2.0v.
The SRC and Trans. Booster seem to work better on 0504 for me, with increased bandwidth.