I've taken a different approach that is working very well. One kick-*** 80mm fan (salvaged from an old server so I don't know the CFM) mounted on the PAL6035. It has an 80x80mm vent out through the side panel. The fan sucks air from the heatsink and exhausts it outside the case.
Think about it -- the major source of heat exhausted directly outside. I also have a bottom fresh air intake and a quiet, low-cfm 2nd exhaust high up in the back. I have the big cpu fan wired to a 7v/12v and normally run it 7v (as it is right now). Right now temps are: room 19C, mobo 21C, CPU 36C (SETI running, plus browser, etc.) Currently my Duron 600 is @ 850 (8x106).