How much more sound can I get?

You'll get a lot more sound! I had 2 chamber flowmasters with a bassani catted x and it was too loud for me. I don't mind a badd-azz sounding stang, but sometimes I just wanted wished I could quiet it down to could carry on a conversation, listen to music, hear myself think, etc... The problem was more than just "volume" because was a lot of drone with that combo (I'm sure youknow what I'm talking about since you already have the flowmasters). The x just magnifies that noise even more. Eventually, I swapped the flowmasters for a bassani quiet thunder catback and it cut out a lot of the drone. It's still plenty loud, though... especially with the baffles out :D