Hey,
What price range?
Hard to find a good 4X dually. Not worrying about price, I'd go for either a Morewood Ndiza (if you can find one), Transition Double or a Yeti 4X.
Only good one I can think of right now is a Norco 4X, but from memory I think thats pretty expensive too, maybe a 2nd hand one (good condition) would be a good option. I've seen good ones for $1,600 on RB.
Personal question. What makes you choose a dually?