cool.
If I may make a suggestion I think you'd be really happy with the
Optima HD7100.
Its got the highest lumens and contrast ratio for your midrange pitch and throw(~5000 contrast ratio and ~1,600 lumens). Which are needed for those rear lit windows. It's got all the plugs you should need including the dvi and does the necessary resolutions and formats for the uses ( NTSC, PAL, SECAM, EDTV (480p), HDTV (576i/p, 720i/p, 1080i/p)). It's also well within your price range for about $1,000.
The lamps are also reasonable at about $350-$400 and have long life spans (bout 3000 hours). Which at your tv time one lamp will probably last you about 6-10 years.
For your conditions I'm going to recommend a tension white screen, although silver will work if you have florescent lighting (didn't answer that question). Elite makes some awesome screens that will fit your wall/aspect ratio and work beautifully with that projector assuming you'll have a less than 30 degree pitch (with a ceiling mount on a ceiling less than or equal to 10' high and a throw of 20ft is usually between 15-20 degrees).
I'd recommend any of their Cinetension series.
Here's one for $600, but you can probably find it cheaper if you shop around. It'll also give you about a 50 degree optimal viewing area. You should do a bit of research to know what the viewing angles mean to make sure it'll fit your seating setup. At 25' you should be able to accommodate a 14' couch (avg 3 seat couch length is 7'). That'll leave you $400 for cabling and a wall mountable surround sound system.
This is all assuming of course that you still think a projector is the way to go. You should shop around and see what kind of plasma or lcd you can get in your price range.
