Welcome to the FFH Forum, Bryan.
I don't know the answer to the specific question that you are asking. But, I have found that the seats that come with the "Luxury package" are the most comfortable car seats I have ever experienced. I've taken several long trips without any back pain whatsoever. And this is even with the concept that accompanying the exceptional FFH mileage, there are not necessarily any gas stops for 8+ hours. I do not know if you can purchase these seats separately, but I would encourage you to go back to the dealer to see you if you can try out an FFH so equipped. What works for me may not work for you, but perhaps this could be a viable option.
Good luck and again, welcome!