ThaDuke, give us an update on your project.
I have two points to bring up.
1) You are trying to save $$$, so do not purchase another Black ICE radiator, instead purchase an automotive heater core.
Radiator Heat Dissipation Article
2) If you put your 600Watt PSU under a full load, you may increase the heat output to dangerous levels. For example, I run Folding@Home on my machines at work in the past 3 months I have had to replace the PSU on all my machines with < 300 Watt PSU's because Folding's new WU's put such a load on them. My point is that the PSU's may be rated for 600W but not a continous load.
The solution is mounting a second PSU in a tower style case (to keep it hidden) you can trick the second PSU to come on by splicing the green wire on the MOBO connector to the first PSU green/Mobo connector. Then splice any of the negative wires in as well. This is something I have been doing for awhile now with my higher end machines and I have had no problems.
Good luck.