I am also in the market for a enclosed trailer, and am looking at a 20'as well (no stacker though)
I can go the inexpensive route ($4700) throw some polished aluminum rims on it and 2 SS stripes to match the rig. Or a highend unit which would probably double the price.
I wouldn't use it on all our trips, so it might get 5,000 miles a year, so I am thinking steel inexpensive is a good idea.
I am going to talk to a dealer down the street this week who has a few Haulmarks sitting on the lot.
2012 Showhauler 28'6" Motorhome on a Columbia w/ 450 Mercedes.