First, define "low price range". Second, why do you assume that back wall placemnet is inferior?
Both Dolby and DTS recommend direct radiators located in the rear as opposed to the dopole/bipole on the sides recommended for Pro Logic.
Are these guys wrong? Opinions Vary.
Having said that, back wall is better than ceiling. If you have to go ceiling, use a dipole or else you'll get a pool or sound much like you get with recesssed can lighting. High frequency sound acts like light in that it gets directional and "beamy" the higher the freq. With ceiling speakers, it is hard to get a good balance between the "pool" of sound that you are in/nearest and the other rear that you may not be as close to. Of course, if there are no other people to worry about, sit in the sweet spot and install which ever is easiest.