Okay then...D5 runs noisier (I think), uses more power, and will give you less flow in a watercooling loop than a DDC+, but its fine if you're not like IanY (check on XS
He has 6 pumps, 2 rads, 12 fans cooling the CPU). DDC+ is better, and with an aftermarket top (alphacool or petras, DO NOT GET THE RADIICAL it has bad performance due to lower max. pressure) totally beats the s*** out of D5. And if you're even more hardcore, Iwaki RD30
But they're sorta hard to find and very expensive, and also need either a 12V-24V DC converter, or a 24V PSU to work. Iwaki MD20 also is really good. Okay enough talk about this.
Okay I noticed your 8800gtxs have Koolance waterblocks on them. That is VERY BAD. Koolance waterblocks are terrible, and will destroy your performance. I strongly suggest that you buy some EK blocks. http://www.petrastechshop.com/ekgtxfucowaf.html
Do not get the DangerDen 8800 blocks because they suck as well. EK blocks are the best fullcover block. If you don't mind the hassle, getting a few packs of cheap ramsinks, and some swiftech MC21 heatsinks, then 2 Fuzion GFX or MCW60 blocks would offer better performance, but you need to stick the ramsinks on which I hear is a HUGE PAIN IN THE ASS.
For your CPU block, the D-tek Fuzion is probably what you want. It has the lowest restriction out of all blocks, and performs very well.
For the radiators, heh, PA120.3 is the best radiator, period. The only rads worth buying at all are Thermochills (which are the best radiators), Swiftech, and Coolingworks (swiftech and coolingworks rads are almost exactly the same in terms of performance).