Quiet muffler

One aspect is how loud it is in the car while cruising down the road with the windows closed and the other aspect is how loud it is when the windows are down. For me, I want a much quieter muffler while cruising but don't want to take a chance on buying one that is not what I want. I typically have a local exhaust shop do my installations, so it would be the cost of mufflers + installation. I remember back in the 80's putting some sonic turbo's on my 69 Charger and it was wonderfully quiet but did not seem to lack any performance afterward.