PC Power and Cooling makes excellent power supplies with adjustable fans (albeit expensive.)
I suggest checking out the ultimate PC gadget/hardware "this and that" site out there: www.cyberguys.com
They have dozens of temperature-control devices, case fans, chip fans, heat sinks, fans with speed controls, speed controls for internal fans that mount extenally to your CPU case for easy access, etc. It's a real hot rod site for PCs, kinda like Jerry Raskin's for your PC. They seem to have every "if only there were such and such" gizmo.
I've bought all sorts of stuff there that's also useful for audio -- heatsink compound, nice multicolor velcro ties for your cables, little parts boxes for RCA and speaker wire ends etc.
Great prices, and super people to deal with as well. They put out a print catalog that's a real hoot if you're into parts, I recommend it highly.