the ram will do what it can.
imo, not achieving high ram frequency has to do with the chipset not handling high fsb and ram frequency but not the rams.
otherwise i had a ep45 ud3p which would not do x 2.4 B (strap333) cas5 with fsb of 540+ ish so had to do 540+ cas4, but another board has no pb doing x2.4B cas5...
which mch, mch ref and ram ref voltages do you use ?
690/720 cas5 (tight?) at 2.3 V is sweet ! really. see if they can do spi32m, nonetheless, very impressive.