HJ, in your research it looks like you have put steerable tag and comfort drive on your list of must have. While both are nice, neither would be on my list. Tag tire wear is not an issue and having a steering wheel that self centers is probably nice but it's hard to beat a solid front axle for simplicity and reliability.
What gives Prevost and Newell their good ride is their 10 airbag suspension. The good news is you do not have to spend that kind of money to get 10 airbags as the bigger Monaco's have them and so does Foretravel. I recently did 1900 miles in 48 hours as the RR10S Monaco's handle that well.
I like
Cranky Ape as you get to see what they sold for and some REALLY good deals have come through their site. For $130K you can find a nice 8-10 year old top of the line DP with four slides and less than 50K miles.