You won't gain any power via bi-amping off the same AVR, the Sony fellow had you spinning your wheels.
You have several factors fighting against you trying to get a wider sweet spot. The room is on the small side, so you lack the size required to simply spread everything out a bit (the easiest way to get a larger sweet spot, and one you can take advantage of when you move to a larger room). Your Polks are the typical direct radiator types with wide dispersion, also problematic when in close proximity to walls, which is unavoidable in a small room. I think the best bet for that room would be some sort of narrow dispersion type speaker (typically use horns/waveguides) placed in the front corners and toed in 45 degrees, which would result in a larger, more stable sonic image over more seats.
But, since starting from scratch is likely not an option, I suggest you enjoy your system for the time being, and make your next "upgrade" via purchasing a copy of Toole's book on acoustics/psychoacoustics. Kick back, listen to some tunes, and read that. It will help give you some ideas on what you can do to squeeze the most out of what you have, and what you should do when you change rooms/upgrade down the line.