Another vote for the HST.
Can't comment beyond what others have said really, other than it is a good tractor.
That trailer on the other hand, I would not be okay with..
For starters you said "double 10k axle". While they DO make heavy duty axles that are single tire and 10k rated.....not for $5500. So I can only assume you meant double 5k axles....IE: a 10k trailer total.
A much more common 14k trailer dont add much money, and gives you plenty of spare capacity. With ballast, loader, and an attachment on the tractor I can have my MX weighing over 8000# pretty easy. Which would make me uncomfortable on a 10k trailer.
Also the length.....you wont have any room to move to adjust the tongue weight with such a short trailer......and if you have the loader on, and a 6' bushhog on the back, thats about 24' in length. Can it be done ....sure. But do you either want 4' of bushhog hanging off the back of the trailer and not be able to stand up ramps? Or leave the loader elevated above the ramps and sticking several feet behind the trailer?
Even though trailer prices are high right now....you can find 24' 14k trailers for ~$6000