The Armada makes a great tow vehickle, as you've found while towing your kart trailer. But, it's real easy to overload it. Your max tow rating for the LE is 9100 #s, and the max tongue weight is 910 #s. Keep in mind that those weights assume an empty vehicle (driver only, full tank of gas). So, yes, I think the Armada will tow the trailer you're looking at, but if you start loading it up to the max carrying capacity, you'll very quickly go over max capacity. I personally wouldn't tow much over 7500#s total with an Armada. My trailer weighs about 5500#s, with a tongue weight of about 700#s. If you can believe it, with that trailer, I am about 100 #s over the GVWR of the Armada once I have my family on board (2 kids, 16 and 11, plus the wife), and a few things in the Armada. By the way, this is a common problem with all 1/2 ton SUVs and trucks, not just the Armada. If you really need to tow 9000+ #s, you'd be far better off with a 3/4 ton pickup or Suburban.
Cheers,
Keith