Very few places show projectors. There is a much smaller market for projectors than flat panel displays and while a typical home may have 3+ televisions, the typical home does not have a single projector. To make things worse, a projector display area takes up a lot of space and costs a fair bit of money, often it is not setup properly at all and looks terrible in store, making the sale impossible. Finally, almost all projectors are sold heavily online and stores make very little profit, unless they can sell you the full installation with cabling and everything that goes along with it.
The bottom line is that a home theater setup looks like a movie theater. Depending on how much effort YOU put into the room/space, it can look better than a movie theater, or worse than a movie theater, but the projectors on the market today, starting at $500, can match or rival your local cinema.
They are designed to fill a screen between 100" and about 150" diagonal.
The typical screen size is about 10" of diagonal for each FOOT of viewing distance. So, if you sit 12' eyes to screen, then a 120" diagonal is typical.
Ideally, you want a good room which you can paint dark. Dark blue, red, green, grey, etc. The walls and the ceiling. With dark carpet. No windows, or fully blacked out windows for daytime viewing.
But, people do setups in their family room or less than ideal rooms all the time and while daytime results can be lacking, the nighttime viewing can be very good.
It's unlikely you will be able to go and see anything beyond what Best Buy may have to show you, but you can ask 100 different questions and typically get good answers about what you are looking for without much issue. There are also excellent websites dedicated to front projection that you may want to take a look at.
