I've read a lot of peoples comments and suggestions on deciding whether to go with Towers or Sierra 2 which also spurred discussion on choosing a center Sierra 2 or Horizons. It seems everyone is in agreement with pairing the towers or Sierra's with one or 2 subs.

I am looking to replace my Paradigm system that's 15 years old. Monitor 7 fronts, cc-350 center, ADP-170 rears and ps 1000 sub. I initially wanted floor standing speakers for the fronts but after reading about the Sierra bookshelves I am not sure I would be sacrificing anything if I pair them with a good subwoofer. I was never truly impressed with my Paradigm setup. As far as the receiver goes I already have a Denon 3313 CI. My living room has an opening on each side so the room which ofcourse is not very optimal for a home theater setup so keep that in mind (Don’t have a choice) The room measures 20 ft x 15.5 ft x 8ft (2560 cubic feet). My main use will be watching TV, playing PS4, and most of all watching Movies. Music listing quality is a nice to have but not what I am purchasing the speakers for. Clarity from the center channel is paramount as my wife and I struggle sometimes to understand dialogue out of my current 5.1 system.

After doing a lot of research it would seem three Sierra 2 up front would be an option or possibly two Sierra towers with RAAL and a Sierra 2 for the center. While horizon center seems like a great choice its too tall and would not fit below my tv so that's not an option.

My questions are as follows:

Would I be downgrading my current system going from a tower to a Bookshelf?
Can the Sierra 2's fill my room?
Can my Denon drive them adequately?
What height does the Sierra 2 speakers have to be at? My entertainment cabinet where the speaker would sit on is 29.5 inchs off the ground.
What surround speakers should I pair this with?
As far as subwoofer goes I was thinking about going with the VTF-3 -MK5-HP or possibly get two cheaper subs. Any suggestions.

I would like to get ofcourse try and get the best bang for my buck and will be weighing my options.