Why do extra work? Carol cable is quality stuff and 12/2 is plenty big. You're not going to get a sound improvement with Sound King. Besides, since you used the Carol Wire, it's probably rated for inwall use, something I don't think Sound King is. Plus, custom install wire has a tough jacket made for pulling through walls and taking abuse, Sound King isn't made to do that stuff. You already paid for the cable, just leave it be.
As for the pool table, I'd set it up as a second zone with whatever reciever you decide to buy. That will allow you much greater flexibility in terms of volume, material played, etc.