if i'm not mistaken, the issue is mostly about premature bulb failure. so unless you have frequent failures, it might not make sense to spend more on a UPS than a bulb costs.
most UPS's are power conditioners, i don't believe you need both.
if you're extra picky, look for a UPS with a 'pure sine wave', that way when it kicks in, the electrical output is more similar to what comes out of the wall.
if the projector is the only thing you're going to plug into it, you should be able to find something under 100bux that will work. it only needs to run about 5mins to safely turn off your projector. i opted for 1000VA models, because i also have my HTPC, game consoles, and router plugged into it. this gives me enough time to turn everything off safely, or about 3 hours with just the router so i still have internet during power failures
Displays: Samsung PN64F8500/JVC X35
AVR: Pioneer VSX-1130K, 7.1/5.1.2 audio
Sources: HTPC(Enby), PS3, XBOX360, Wii
Control: Harmony One