$45 and under? Are you kidding? And watercooling isnt silent either. I would stick with air cooling if you really wanted silence. And if you are getting a TT watercooling kit, you are not going to be pleased, i can warn you right now. But if you really want it, i cant stop you. Now, a silent psu. The ONLY one I would personally recommend is Seasonic S12-500 or S12-600. Both of these are up in the 130+ range. I would NEVER get a psu under $90. Just my 0.02, but your decision.
I dont know the OEM for the psu that bob recommeneded, but to be honest, i would stay away from aerocool. There is a whole list of psu manufacturers that i stay away from. If you had the money for the aerocool, dont get it. Instead get the OCZ GameXstream for cheaper and its better. Fortron OEM.
GameXstream is better than the seasonics, and shouldnt be too much louder. To be honest, ill be buying a PCP&C Silencer 610 for 160 bucks yes folks, a pc power and cooling psu for 160 bucks!! 610W of pure power. Its a killer deal. hahah. It comes with a whopping 49A 12V rail. And 83% efficiency hahaha. Yes yes yes. I am sooo happy. but yeah, back on topic.
Get the OCZ GameXstream 600W. You will love it to death.