I shouldn't think the air flow would make a lot of difference to temperature - it will be no more than a few degrees above ambient, and the heat transfer from it to a plexi reservoir will be negligible - unless you're going for massive overclocks you are unlikely to be able to tell the difference.
If you're interested in quietening it down, it might be worth replacing the 80mm fans with quieter ones, depending on how loud the pump is in comparison. Still, I am a quietness freak
