Agree on Sumos.... they can soften the ride and there are different weight ratings.
I have a Class C but also hated the ride quality and noise of bumps, expansion joints, etc. I installed 500lb rated Sumos for the front and 1500lb Sumos for the back. The ride was noticeably improved.
The other option for my rig was 1000lbs for the front and 2800lbs for the rear and I thought that would be too stiff.
Your other options would be better shocks and / or airbags.