I do not know exactly which models are available in the USA, but the BMW X series with the 3.0d engines are very capable haulers and get upper 20's with a trailer if you don't stomp on them too hard. I have an X3 with that engine, and I have heard at least you could get the X5 with it in America.
I just pulled about 800 pounds of cargo in a decent sized trailer and got around 27 coming home, 75mph the whole way.
Plus side is that when you take the trailer off, the thing is hella fun to drive and gets around 30 on the highway. You also get all wheel drive and decent ground clearance.