Ive only tested them with those ballistix.... I think this board just sets the PL level lower than the Asus or Gigabyte thats why its harder to hit high mhz... Ive seen P5Ks with PL of 9 or even higher whereas with my board I cant remember even seeing PL=8....

It does take alot of vdimm to hit 600+fsb cas4 though and I think thats where the ballistix 5300s have a big advantage over the Dominators.... Its alot easier to beat up cheap rams