Well airspirit you've inspired me to do a similar project. Only mine will be used on one comp, but will be flowing through 2xHDD water blocks as I have 3 HDD, a vid block, CPU, and northbridge block. This is what I have so far.
Also I picked up a Lifeguard Quiet one pump for cheap. Here are some specs:
HP: 1/25hp
Max Flow: 1140
Shutoff Head: 15'
inlet: 3/4-1/2" (adapter)
outlet: 3/4-1/2" (adapter)
watts: 87
color: white/blue
I don't really care for the wattage on this pump compared to the Iwaki, but I think it will do the trick. I tried to run my Eheim 1250 with the Lytron rad last night and the flow was non existant.