If by "in-wall" you mean no footprint but (1) the speakers can be on-wall so long as they don't stick out, (2) you can make an exception for a subwoofer, I strongly suggest you look at the Magneplanars. The units I'm thinking of are flat panels about 3 feet high by 10" or so wide by an inch thick and are mounted vertically to the wall with hinges, so when not in use they can be turned back flat. Center channel duties are handled by a pair of MMG-Ws, one each side of the screen; surround and rear are two more pairs of MMG-Ws mounted on your walls the same way. The front channel duties could be another pair of MMG-Ws or, for a bit more, MC-1s, which have treble extension up to 24KHz. You would still need a good subwoofer, though. You didn't state a price range, but the Maggie-plus-sub system I'm describing would go for from $900 for 3 pairs of MMG-Ws to $1800 for the MC-1s plus 3 pairs of MMG-Ws for 7 channel service. Plus, of course, the subwoofer. (You wanted everything in the walls, but does anyone make in-wall subs?)