Yeah i know what you mean. The only problem with replacing the fan, is it would work off the same engine. You know what i mean. So in other words, it would be a bigger fan working at a pretty slow rate. But, if you have a 120mm fan on your removable side panel, then you would be getting about 75% more air for the stock fan to work with.
For that type of MOD, i dont think their would be a real benefit. I would suggest a PCI cooler, and the 120mm fan on the removable side panel. That way theirs alot more air for that fan to kool that heatsink.
But if you wanted to get real technicial, you could make a 120mm fan"Container" then MODD it in your case somewhere, so its blowning striaght onto the heatsink itself. But i do think that the stock zalman fan, would still work good. Just the way that heatsink is desigined around the fan.
Finished With TF.