Welcome to the boards. The Z will be a huge leap forward in terms of generally everything (except, maybe, power).
Regarding the exhaust, the Z, while it's one of the louder cars on the road (in terms of road noise) the exhaust is very quiet. You don't hear it while cruising but you can hear it when you get on it. If you find the stock exhaust is too quiet and want something a little louder when you get on it then you might want to check out the NISMO cat back. It's generally very quiet and civil but it's a little louder and deeper when you do get on it.