Need help understanding throw/offset specs

Well it's tax refund season, and once agian I'm getting projector fever. For the last couple of years I've been on the fence and almost pulled the trigger, but even after researching, I've never been able to commit. Everytime I think I've found a projector I might like, it always seems to have an achillies heel.
Here's what I'd like to get-
Something that's not over $1000
3D not important
The best black levels I can get for the budget
A 110-120 in image

The mounting always seems to be the roadblock. I've tried using the projector calculator, but there's some things I can't figure out. What I'm looking for is a projector that can give me my desired image size that can be mounted as far back in my room without having the image nearly on the floor or on the ceiling. I live in an apartment so my mounting options are somewhat limited. My room is about 15 feet long with an 8 foot ceiling. Can someone help me out here, please?
The more I research, the more my head spins, lol.

Thanks for the responces. The projector calculator site you linked to seems to be broken now. That'll teach me to write stuff down I guess. I tell you, projectors might be more than a niche product if the placement options were a little more flexible in the budget range. That's always been a deal breaker for a lot of us.

You may not think they are if you have one. But seriously, how many people, even people who consider themselves serious A/V hobbyist own a projector compared to flat panels? C'mon, it's a small percentage and you know it. And I don't mean to belitle fp by calling it a niche, after all I'm looking to join the club by asking for help. But lets be realistic, it's a niche.

For arguments sake, I'll just say they're not mainstream. In fact, that's part of the appeal to me.