No problem. How good it sounds is another thing altogether. I've yet to hear an in-wall that can hold a candle to a stand-alone. It just depends on where your priorities lie. If you're going to crawl up in you attic to wire the surface mounts, you might as well drop some wire into the walls, terminate them with Niles plates, and enjoy the superior sound of a regular speaker. You'd want to do this for your center channel anyway so why not go for the trifecta? Will it be as indiscrete? No. Will it sound better? You betcha. Again, it just depends on your priorities.

Good luck and have fun.