I'm in Forsyth too. Never used any places around here though, sorry. Interested in your feedback on whatever shop you choose, and how it sounds sans muffler.
The Muffler Shop in Buford. They are a full service mechanic, but they specialize in exhausts. Hands down, period, the best. Nate is a solid guy. They replaced the bevel box and rear diff on my R, and I would trust them with anything.