I put Road Kings on just under four years ago. They improved the handling while stopping some front end porpoising. These were the previous generation, and the new ones are even more robust.
Rigs with front IFS, will see the most improvement.
I do feel that Koni Adjustable or FSD's on the Drive and Tag, with Road King handling the IFS - could work well for those that want to save some coin.
I have not been to Premier, but I've read positive posts about their service. You might take a look at RV Service Review, and see what may be posted about them.
Roo II is our 04 Country Coach Allure 40'
OnDRoad for The JRNY! Enjoy life...