The Intel cooler delivered with the Core 2 duo E8600 was a nice surprise to me for being silent and compact.
I had purchased an Arctic Freezer 7 Pro even before receiving the Cpu, but this cooler isn't as good as the excellent Arctic I have on my PIIIs Tualatin: much louder than the Intel cooler.
As I plan to push the E8600's clock a little bit (but remain in air cooling and quiet operation and safe voltages) I'll probably need a more efficient cooler than the original one. So as Intel's cooler seems good, I consider the simple solution:
Take an Intel cooler delivered with a Core 2 Quad and put it on my Core 2 Duo.
My mobo, Ga-ep45-ud3r, accommodates Core 2 Quad Cpus as well, so I expect no compatibility issue. After all, both coolers look the same, the Quad being just taller. Maybe the fans even rotate at the same speed, do they?
It's clear that the original C2D cooler isn't good enough to overclock a C2D, as is clear that an original C2Q cooler won't be more silent than the original C2D cooler. Though it is already surprisingly good, I'll look for an even quieter one than Intel.
One more point: I wanted a cooler that I could secure without access to the rear side of the mobo, so that I could replace the cooler with the mobo in the case. This was a mistake. Mounting the cooler requires to push so hard on the pins that you want to hold the mobo by yourself, not at a few points.
Finally I've tried in real situation the Freezer 7 Pro from Arctic Cooler I had purchased. As I had listened at it without speed regulation I was disappointed, but with speed regulation, this C4Q cooler never gets fast enough to produce noise with my C2D, not even during bootup.