Just with the rear muffler only, I'd be looking to get either a stock muffler or a as close to stock as possible option. I had the rear muffler changed on mine, with stock headers/Y-pipe, and the drone was HORRENDOUS. Bad.

Replaced the headers with HM and the drone went away.

I'm not sure what brand/model muffler was put on, for reference, but it's a straight through thing and quite compact. I'll post a part number in the morning. If you just want to do the rear muffler the one that's on my car would be one to avoid.