Looking for opinions on both running a dual loop in this one particular instance (saw the thread on single vs dual), and a way to mount dual D5 pumps in 2 isolated loops if things head that way...

Issue is this... in a C70, the flow goes like this:

Bay res -> D5 -> bottom intake rad -> CPU -> GPU2 -> GPU1 -> upper exhaust rad -> bay res again.

Airflow bottom to top

Hardware:
Raystorm, 3770K, delidded, 4.8Ghz LinX all-day stable if water is 32C or below (creep past 32C and WHEA errors slowly pop up. ivy seems very temp sensitive.)
2x 670 GTX with EK full cover blocks
2x Swiftech MCR-220XP radiators w/ corsair fans (SP version)
Vanilla D5, variable
EK spin res

Problem is this... there seems to be a recycling of heat with the lower radiator dumping heat into the case and back into the upper radiator, or at least hampering it's performance. (using thermal probes for intake air, internal case temp, water temp, top exhaust air temp) Water temps slowly build during furmark to 36C max (26C room temp). Case temp builds right along with it. Internal ambient temp and water temp are basically the same most of the time. Taking the side panel off helps. I'd like to keep the water-to-CPU temp below 32C. 36C is fine for the 670s.... they barely peak at 45C during furmark at 5760x1200 8xMSAA

Issue is me, really. Hate dust and only want filtered intakes on the front and lower part of the case. Do not want to add external filters to the case and like the stock C70's filters. Flipping the top fans seems simple enough... but all that heat from the 2 670's going down into the case seems less than ideal when it can go right out the top (and having 6 intake fans with one exhaust on top of that.)

Was thinking... split the loops... and have the 670s dump their heat out the top, and keep the CPU drawing off the bottom for cool air. The heat from the CPU loop will pollute the GPU loop but they're beyond cool enough as it is and the CPU would be isolated to the coolest water temps.

Thoughts?... pic of setup below... was thinking of taking out the last hard drive bay and mounting the SSDs elsewhere for more space as well. This thing will never see a mech drive. No need for that huge cage.