best mufflers for new Challenger?

Corsa catback exhaust. Not cheap, but sounds really awesome. You can check out alot of different exhaust sounds for Challengers on Youtube.

If you want it louder,
instead of changing the mufflers
why not run
a tube from the engine compartment
under the dash to the interior
and maybe even
fit a stopper on the interior end
so that you can have it open or closed?

I know it sounds crazy
but that is what BMW did
on the Z4

Have all the noise you want
without disturbing the neighbors.

Might even improve your fuel economy....
based on the theory that most people drive
loud cars a little slower,
and silent cars a little faster.

After suffering thru the cat-back magna-flow system on my Magnum I know what not to recommend...unless you want LOUD. You could probably just drop the resonators and it'd sound fine.

Getting the wrong system will cause a bad drone at speed especially with MDS active. Borla or Corsa are the best but most expensive.