Just add a second layer of drywall to all walls and the ceiling. If this room has another room above it or below it, that is where you'd really want to beef up insulation. And accessing the floor and ceiling will make running speaker wires much easier.
Go on Amazon and buy whatever size Panasonic Plasma you can afford, particularly the last remaining ZT60 models! (ZT and then ST are your next best in order) And do it soon, they're discontinued!! But arguably to the best possible picture you can get for the money!
Unless your seat is all the way against the back wall, (which I think would sacrifice much of the performance of 5 tower speakers) you wouldn't benefit much from front projection.