after seeing your current setup , if i was in your current position my decision would be to keep my current trailer.
toyota products are excellent . we have had 2 avalons and 3 lexus v8 sedans since 1997 . trouble free , quiet , and nice to take a trip in for Interstate driving .
because of our german sportscar we got spoiled by the best handling cars on the planet . we live near the Cascades and drive 140 miles on curvy 2 lane highways before we can be on an interstate . hence the switch to the mercedes sedan .
an audi , vw , or benz diesel suv would be a nice upgrade .
but each of those will be way less than capable towing a 22 foot trailer.
however with your nifty 18 footer they would be good .
for very little money i would try upgrading my dining fly , camp stove and other camping necessities .
that would be way less money than a 22 foot trailer upgrade , especially if i would have to go even bigger in the suv (escalade, denali) to tow a 22 footer .