The 2007/08 Jeep Grand Cherokees are available with a Mercedes diesel in them, same V6 diesel motor the Mercedes ML's that Westend suggested above have, should cost a bit less than the actual Mercedes SUVs, while still a pretty nice/fancy ride. If I recall they are rated to tow something along the lines of 7500lbs, and have a decent carrying capacity too (around 1300lbs), should pull a trailer like yours with ease, and get you decent mileage doing so, I hear they get about 25mpg hwy empty, and I would bet about 15mpg towing a trailer like yours.
Our Jeep Liberty has a VM-Motori motor, which while reliable, is hard to get parts for locally, most have to be ordered, and then finding a shop who knows how to work on it is a bit of a pain, thus our main reason for upgrading. The Mercedes has a bigger presence here in the USA, that motor is used in all the Sprinter vans/RVs and Merc's passenger vehicles, so parts and skilled shops are a lot easier to find.