What is your CPU voltage?
as for your 8800Ultra's I have that same water block on mine and i hold 42c Idle and about 55c load.
I checked on 5 other 8800's w/ the koolance block and they all are all 40-45c idle and 55-60 load.
the only two things i can see effecting your temps would be the water loop flow path and thermal paste.
also the tubing between both 8800 can be replaced w/ a sexy 3 slot koolance interconnect nozzle.
Dual VID Connect Nozzle, 3 Slot Spacing - Water cooling systems, pc liquid cooling kit, cpu, video card, hard drive
We have a QX6800 running with a CPU-330 block in our office and ill take a look at the temps a little later.