I have the Embark which is basically the same chassis except with the bigger 8.3L Cummins engine. I also had an 07 Seneca. The driving of this truck is so much better than the old Kodiak 5500 chassis. If it has enough power with the 6.7L engine for you, you will like it. I felt the Seneca has a better power to weight ratio than the M2 even with the 1000 ft.lb. 8.3L.
I really like the M2 chassis and would buy another but not the Jayco part of it.
Did you look at the new Dynamax or the Renegade?
Good Luck