i'm wondering a similar thing. I already have two UPS's. one at the front of the room for the receiver and sources, one at the back for my HTPC and HDD's. I would like to get one for the projector, but i have a plug on the ceiling, and there's a huge difference in weight and size between 300-400w vs 600+
my other concern is that i when i bought my new tv(64" f8500) it uses so much power on bright scenes that it was overloading my UPS at the front so i had to change it from a battery power plug to a normal surge protected one. so whether or not my projector only needs to have the fan powered, it still needs to support full power for when it's in use. it won't do me any good to have to plug the projector into the ups AFTER the power failure just to get the fan to run. that makes no sense.
my question is, if a projector is rated at 375watts(or whatever), does that mean 'typical' or 'max' power? if that's max power i can get a 400-450w ups that is small and light enough to sit on top of my projector. anything more than that really needs to be on the floor/shelf.
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1130K, 7.1/5.1.2 audio
Sources: HTPC, PS3, XBOX360, Wii
Control: Harmony One