Mr Target has explain exactly what i shall be doing with my setup. I'm moving from a Coolermaster Centurion (cramped for WC) to a TJ07 (spacious).
I have a C2Q and 8800GTX in SLi with a PA120.3 rad (with Yate SL fans) cooling. At stock clocks in the current british summer i am seeing 63C at load and 75C when at 3GHz.
My GTX will pump out more heat than your GT given its revision but your rad is no where near what will be needed. When i was CPU only after a few hours the system would reach 70C by heatsoak from the GTXs but at 3.8GHz before heatsoak could take effect it was 35C at load. This shows you the heat load the GPUs add to your loop (another 35C at least) and that is with the biggest and best rad available. The GTXs run 74C at idle with stock cooler and thermal cut out is 110C so expect heat issue when your GT is connected.
When I move to the TJ07 I will have 2x PA120.3 as that is the only way it will cope with the heat load. Have a butchers at my thread
If you wanna see my problems.
Your best bet is a second rad between the CPU and GPU as Mr Target said but the GPU will give more heat than the CPU so make sure its the biggest and best you can fit in.