I submit that Chrysler is reporting over 31,000lb GCWR on a properly equipped Ram3500...that should tug a 20K 5er very well.
While the spectacle of a Medium Duty (C4500/F450 and 6500/650) or Heavy Duty Truck (Class 7 or the REAL overkill, Class 8) might seem attractive, the cost is prohibitive.
And...who wants to use that kind of monster as a daily driver or destination vehicle?
Why do you think RV Hauler is hanging Smart cars (sideways) on so many haulers...BTW, at over 106" bumper to bumper is actually a wide load
Toy Haulers are misunderstood by those that do not have them. The over-hitch section sleeping spaces in a 5er and any lofts are always useable - Toys loaded or not. And in particular, the 376TH master suite is over the toy box, and never impeded.
To the OP, whatever you get, hope you share all about it.
P.S. We put our Smart inside the toybox...fits great!