Go with a Trooper/Rodeo. Like everyone has said, the 4500# tow rating is just that a rating. The Amigo can handle it, but it is not recommended. The short wheelbase means that the Amigo is much more likely to be dragged around by the trailer, then by it being in control of the trailer.

The Trooper/Rodeo (93+ on Rodeo, 92+ on Trooper) would pull the load you are talking about much better. It would still be high on their tow rating of 5000#. The rating is just a number....I have always heard a good rule of thumb.....the true towing capacity is roughly 80% of what they list for anything over the highway for long distances, and 90% for short distances.

[EDIT] When I say Trooper/Rodeo, I mean they will tow better because of their wheelbase....however like Jeff says below, they are not the fastest when they are loaded down