I'm not much help on the MTH Challenger but after talking to experienced customers with other MTH HO loco's, I'm not sure I would mess with one. The biggest complaint I hear is that there are a lot of features that activate on their own and are not controllable unless you have their DCS system. You can not access all the features with DCC.
I would personally suggest waiting for the Athearn Challenger that was recently announced. I do have experience with these. I have a friend with both the Challenger and BigBoy from Athearn, with the much maligned MRC decoder in them and they are still going strong for over 5 years. They get run a couple hours a week every week and pull 40 car trains when doing it. The new versions come with a much better decoder and they are even offering a DC version for the first time in this batch if I remember correctly. They will go through a Bachmann EZ track standard turnout (18" R) but you need to watch clearance due to the overhang of the loco. They will also go through 18" radius curves but they are not real pretty doing it and your track needs to be perfect as that is pushing the limits of the loco.
Athearn Challenger On 36"R curves.....
