On a basically stock car with bolt-on mods, they'll all make close to the same power. There might be a difference of 1 or 2 hp tops. Basically it's up to preference.

Here are the main "quiet" exhaust choices and their differences:

A'PEXi WS - polished stainless muffler, flat black mild steel pipes


RS*R Exmag - flat black stainless muffler w/ polished tip, flat black stainless pipes


GReddy SP2 - polished stainless muffler, polished stainless pipes


Tanabe Super Hyper Medalion - polished stainless muffler, polished stainless pipes


Personally I'd limit my choices to the ones with stainless pipes. Of those, the Exmag is the quietest. The GReddy and Tanabe are really close, with the GReddy being a tiny bit more mellow and the Tanabe being a tiny bit more raspy. All of them are far from being a typical fart-pipe sounding canister system.

I guess the DC TCS fits in the quiet category as well but it's a good bit more expensive.