With your room size, a 5.1 system would be more than sufficient IMO. I would do some more digging into speakers that are not sold at your local Best Buy or equivelant. I would audition systems at dealer only distributors with your speaker budget. One, the sound rooms tend to be dedicated and a little more conducive to a fair audition and they usually carry the next step up in speakers that you would not find at the places you mentioned. Revel, PSB, Martin Logan, Klipsch, Paradigm, JBL, Infinity, Athena, Energy, and many, many others. Maybe you can find a local audioholic to listen to Axioms and the RBH line.