[jtroutma]

Here is what I would do if I was in your situation:

First, how much are you willing to spend? I ask this because you can do may different combos:

Straight silence, low cooling performance
One radiator with fan @ 7V

Mostly silent with better cooling performance:
Two radiators in parrallel with fans @ 7V.

Not so quiet but better cooling performance:
One radiator with fan @12V

Little bit less quiet than previous but even better cooling performance:
Two radiators with fans @ 12V. (better pump would be in order here).

In any case I would setup the blocks in parrallel with eachother useing "T" lines setup the way the picture shows down below.
The line size would probably be all 1/2" but you could go down to 3/8" to each block from a 1/2" feed line. All up to you.

This may not be the most efficent design but maybe one of the simpler ones.