There are some very nice (and expen$ive) in-wall options. That being said, I've never been a fan of in-walls for anything other than surround duty or background listening.
First, it's usually difficult to mount them low enough for an optimal listening experience - they most often end up 5+ feet off the floor.
Second, you have no ability to move them closer to, or away from the wall, or toe them in or out, etc...
And lastly, you often end up with some nasty resonance within the wall itself, that is very difficult to tame.
However, if it IS your only option....:-)