The OP proposes getting a 7800# TT but does not note if that is GVWR or "dry weight". Moving on beyond the fact that "dry" weights are useless, often dangerous jokes we need to know which he is contemplating. A 7800# dry weight TT will likely weigh in a lot closer to 10,000# in the real world in which case using an Armada would be a disaster waiting to happen.
If the GVWR is 7800# the Armada will be at its absolute limits and towing that long of a trailer with that short of a wheelbase will not be particularly fun, much less safe. With a smallish SUV staying at a GVWR of no more than 6,000# sounds like a good plan to me but...
As always.... Opinion s and YMMV
:C