Not for sure on the sound. I have SD Headers/catless and I have a bit louder tone but with factory res and mufflers its still quiet. I do need a better resonator as mine is more raspy than I'd like. But either way it won't be much louder, slightly but not very much.

As for the adapters I wouldn't think you would need it. A good exhaust shop should have the tools to stretch the pipe out to make an adapter should the need arise. Just be honest with them up front that way they can check and be sure before they cut it out and leave you in a bind.