Case Fan Solution?

I'm OCing my Athlon XP, at least I think I am. I went into the BIOS and used "Load High Performance Defaults" and it jumped my clock from 1.25Ghz to 2.08Ghz. So I'm assuming its like a built in overclocker. Anyway, my temps were going up into the mid 60s so I bought a VANTEC Tornado and that brought them down to 44C at idle and 55C under load.

I want to preserve my CPU and possibly overclock it a little more, but I'm nervous about buying a new heatsink because I ruined my last CPU replacing the heatsink. So I was wondering if I could just purchase a more powerful case fan the same size as the CPU fan (60mm) and screw it onto the heatsink. Or would that be a bad idea? Any advice?