Main specs of importance w/ projectors that can vary greatly, model to model is: Contrast ratio, and lumens (light output).
Cheaper projectors are much dimmer than expensive ones. Also color temp is important to many. Nice ones may have expensive 5500k metal halide bulbs (same color temp as the Sun) in them to produce vibrant whites that halogen can't produce due to it's 3000k color temp. That's w/ LCD ones. DLP projectors are different altogether. I don't know what DLPs use for lightsource, whether it be a bulb or what.
I'd make sure you test the one your thinking about, in the store (at the desired screen size you will want to run it at in your home), and make sure your happy with it before leaving the store. Because a lot of times, they show you at the store on a small size like 15 or 20 inch screen, which will make quality and brightness much, much better, when the reality is that when you expand that size to the 50-100+ inch or whatever size then it gets way dimmer and quality goes out the door, directly perportional on an X to Y curve of distance/screen size to quality/brightness. More of X will = less of Y.
Or another option, is go buy one from Costco, since they have an AWESOME return policy. If the given store will let you return it just because of dissatisfaction alone, then go ahead and try one. But if they wont let you try it first then don't get it, because you gotta make sure your happy with the performance before you marry yourself to it, especially with projectors because there is so much variance in performance, model to model
