The two projectors that really come to mind for me are the BenQ HT2050 or the Sony HW45ES. There is a sharp price difference between these models and the Sony is a bit over budget, but is what I would go with in a good dedicated space.
The BenQ is on par with the models in the $1000-$1500 range, and there really isn't something better until you get to the Sony. Epson has some brighter models which perform better with some ambient light, or if you need a lot of placement flexibility, but that doesn't seem to be an issue for you.
Short throw doesn't typically make sense if you can avoid it. The screen requirements are tighter and the optics of short throw, while they are very good, can cause some image issues not typically found with longer throw models. So, I would stick with a standard throw projector.
You can read reviews of both the BenQ HT2050 and the Sony HW45ES online at any number of places.
I think a questionable step up would be the Epson 3100 or Epson 3700 both of which I think aren't really better performers than the BenQ. They are brighter, but they don't get better black levels, and they aren't going to outperform in other areas.
The Sony is the real jump in both black levels and overall performance and build quality. It runs nearly silently and should have no issue filling a 120" to 150" screen diagonal.
Room layout depends a lot on your desires and needs. There is a lot online of examples of theater setups, and how much effort you put in, or want to put in, is up to you. Tiered seating, wall sconces, lighting effects, etc. are all great, but very person to person dependent.
The rules on screens are pretty standard these days: About 10" to 12" of diagonal for each foot of viewing distance.
Get a 16:9 screen unless you are really knowledgeable about doing a different type of screen. Plan on 16:9.
Lighting should be broken into multiple zones of lighting on dimmers. Lighting over seating area should be very directional to provide lighting to move around, read, or perform in-room tasks easily, without casting any stray light directly on the theater screen. This is the lighting which allows you to 'hang out with the guys' without being in a pitch black theater space. Great for sports and eating popcorn.
Any windows or sources of ambient light should be covered with light blocking shades or draperies. Don't skimp on this if you want it to look nice. Though, I've seen people just cover it with cardboard to keep the light out. A good set of light blocking shades isn't the cheapest thing in the world.
Finally, consider the room color. A proper theater is dark. Dark ceilings, dark walls, and dark carpet. Hardwood tends to reflect both light and sound in uncontrollable ways creating a very 'bright' room for audio, and reflects more light onto the screen decreasing contrast.
Please take a look here for some information on lighting considerations and impact on the screen. Make sure you put in MORE lighting if the room is darker. You can turn lights off easily enough, but adding light to a dark room after the fact can be difficult.http://www.avintegrated.com/lighting.html
- Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.