As far as my testing goes CAS2 2.5 or 3 doesn't make any difference at all. I haven't done any clock to clock comparisons with these sticks yet but you'll see if its faster than BH5 in 3DMark
(282x11 (CPU limit w/ 11x) 1:1 should give a nice improvement over my current score)

btw, superpi 1M passed at 291.5MHz 1:1 3-2-2-8-8-16 now - default heatspreaders no extra cooling..