Going from a low walled trailer to a high walled trailer is significant. There is a lot more air resistance which means more power, fuel, and heat. If you want to keep that MDX, then I recommend sticking to under 3500 pounds GVWR (single axle) TT. Also, flush all the fluids and install a heavier duty transmission fluid cooler. If you want something heavier and high walled in the 5000 pound dry range, then I recommend any half ton SUV. Something with at least 6-spds in the transmission. Pick your favorite brand, but again you need the HD trans cooler.
Brand does not matter with respect to quality of construction and assembly. They are all about the same (not good). If you are handy and experienced with your prior RV, then I recommend never visiting an RV dealer for repairs/maintenance.
Historically, you will find the best prices for new RVs in the midwest. IF you are willing to drive to Ohio once to pick or NY, there are some "Wholesaler RV" dealers that offer discounts around 30% off. Check out RV Direct for example.