This might be slightly OT...
Its an idea I had based on my limited experience of water cooling, where two pumps might be quite useful.
In this case, one pump is driving the "main" cooling loop (CPU, GPU, rad), and the second smaller pump would drive a "secondary" low flow circuit to cool lower power components such as hard drives, northbridge, mosfets, PSU...
The main loop would be 1/2" or 3/8".
The second loop could use 1/4", which has the advantage of being that much more flexible
Excuse the lame paint hack of your wonderful diagram
