I only have one suggestion. Vance and Hines Cruizers!
If you cruize on the X, this is for you, (or him).
Great sound and they look good too. The baffles are fiberglass wrapped and kills that raspy sound no one wants. They do get loud when you roll the throttle, but sound mellow when cruizing.
Vance and Hines did some good reseach and development on these pipes. The big shots sound good, but a little louder than the cruizers.
I have 24000 miles on mine and that just my $0.02 worth.
The classic 2 into 1 are a smitch louder than stock and have a good deep sound to them.
I have had them on my 1800 for 4 years now and would not consider going to anything else. I do not like loud but I do like a deep rumble.
The dually's are louder because you have a pipe on each side of the bike.