The vast majority of projectors top out at 800 by 600 resolution with a few going up to 1024 by 768. Really high-end units can handle higher. Pretty much any video card will support those resolutions. Another consideration would be whether or not you need additional inputs such as a DVD player, HDTV receiver, etc. Watch the specs of any model for input options.
One specific thing you'll want to research has to do with the flicker introduced by the colour wheel in each unit. I don't know all of the details but apparently, some people are quite prone to seeing a flicker created by the colour wheel. Spend some time with each projector you are reviewing and be sure to turn from the image and watch for the flicker out of the corner of your eye. It may seem silly to worry about something you might not really notice when focussing on the image, but it can make your eyes quite tired and give you a nasty headache.
Good luck...