1. Front ceiling speakers are not going to work well, and should be seen as an absolute last resort.
2. If you don't have an AT screen, you can't put a speaker behind it, regardless of the volume.
I would go with some bookshelves on each side, and then get a center speaker stand to mount the center below the screen and tilted up.
If you like the Paradigm sound, consider some of them, a pair of Mini Monitors and a Center 3 would make for a nice sound stage. And seeing as you have a sub, there won't be much of a drop off in sound compared to towers.
Samsung PN60F5300 | Denon AVR-1713 | EMP E55Ti | EMP E56Ci | EMP E5Bi | Outlaw Ultra-X12