I have a computer that was lying around collecting dust so I decided it was time for boxee.
At first, the thing was intolerably loud. The hard drive resonated/buzzed in the case and the fans sounded server-ish when playing hd video. The corner where the computer resides is also noticeably cooler, it used to get HOT.
Now the computer is so quiet I have to look at the lights to know if the computer is on (even when the house is totally still).
The list of changes I made:
-Replace stock cpu cooler with a heatpipe from an old dell. The fan now runs at idle with temps hanging between 82 and 102f.
-Remove video card in favor of onboard video. This cut down noise and case heat dramatically.
-Replace the 3.5" hard drive with a 2.5" laptop drive. Again, heat and noise are reduced. I put in a secondary 3.5" 500gb seagate in for local media and set the spin-down time to 5 minutes.
Obviously this could be taken further using SAN for bulk storage and SSD for the OS, silent power supply etc. But, for only costing me a spare 2.5" drive and heat pipe cooler which are inexpensive parts to begin with, the results are great. My only gripe is that ATI+Flash video has been a real bummer. If I had a choice I would have liked to try nvidia instead.
I'll post a video of it running if anybody is interested.
Athlon phenom 8450 triple core
Onboard Radeon HD 3200 w/ hdmi
120GB 2.5" HD 500gb 3.5" HD