The size replacement fan you should be looking for is 60mm, this is the Cooler Master HHC-001 right?
The current fan your using sounds too be the the famous delta ScreEeeEAmER! (46.5db / 36cfm) I feel your pain those are very annoying fans, i can't stand em

The 5500 RPM one your talking about is most likely the slower version of that the Delta 39db / 30cfm, its not really that much of a difference but i guess if your used too the screamer then you'd probably be able too tell, over time you'll find this one too loud too.
If your not overclocking, you should be able too back down too a very quiet fan like the Sanyo Denki H speed, its 28db / 21cfm. It may not seem much but the cooler master heatsink is a big heatsink so your CPU will be comfortable with this slow of a fan. (i've seen this heatsink equiped with a 14cfm fan)
Reason why i recommend the Sanyo Denki is it blows its air out very strong, more then it actully feels (high pressure) perfect for a HS, and the quality on these fans are really great. Do a search on the for sale forum for quiet 60mm fan.
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