You're definitely invited to buy me the stuff to test with, tw.
Honestly, everything you say is absolutely correct. I simply do not want to take any risks with my setup, so I'll be using good thermal paste.
As for CFM and the like not mattering - regardless of anything else, the fact remains that if I blow lots of cold air on the heatsink, it will help to dissipate the heat (er, this is a fact, right?). If I'm putting plenty of cool air on it (and getting rid of the warm air), I'm helping to keep it cooler and thus prolong the life of my processors.
My Dual G4 800MHz doesn't have a fan on the heatsink - just a pretty good-sized heatsink. Passive cooling. Works rather nicely, and the heatsink just gets "warm" - not "hot". I suppose it's all just a matter of chip design, though. AMD is racing with Intel, and so they put forth technologically inferior designs that consume more power and thus produce more heat. IBM & Motorola are competing with no one, so they take their time and design low-power processors that are still quite zippy.
Regardless, I think that what I have ordered will do just fine, so I'm not too worried about it. My concern is keeping the box running, and these should do just that.