JC, welcome. The Epic 80 7.1 would be an excellent choice for your HT setup, but a significant step up would be getting the VP160 for the center speaker.
The assumption in getting a 7.1 setup would be that you have enough room behind the seats(say at least 4')for an effective rear sound field to form. Those sitting right up against the wall would get little or no benefit from back surround speakers. So, on this point it isn't the size of the room as such that's significant, but the space available behind the listening position.
As to the receiver, the SR7005 would certainly work well, but I suggest that a similar Denon or Onkyo unit is more cost-effective. If you'd want to stay with a Denon/Marantz product the very similar Denon 3312 available as a factory refurb from Accessories4less
here for about $650 can be recommended. An excellent Onkyo unit of the same class(except quite a bit heavier)is the 809 available from A4L for about $600.
