Since the theater area is flanked by one wall, I would treat that wall for acoustic symmetry. Put a broadband acoustic absorber on the wall next to the screen.
If you wanted to go nuts, one thing you could do is get an
all Monolith THX system. It would have pretty good performance for the money. Monoprice has put out a very high value and high-performance home theater line. you could get an HTP-1 processor, Monolith amps, Monolith THX speakers, and some Monolith THX subs, the ported 15"s or even the ported dual 15"s if you want to get nuts. With the HTP-1, you could get a 7.4.4 system and have all the components independently calibrated by Dirac Live. An all-out, all Monolith system would probably run you something like 25 to 30K, especially if you went with the dual 15" subs. Order everything that you need from Monoprice might make it all simpler for you as well.