For $400, don't expect that much. The QU-BD TwoUp was made for those on a budget. It lacks many features which almost all others have, such as simple endstops to home the extruder, a heated bed, and easily upgrade-able electronics.
The Printrboard electronics which it use only support a single extruder, so to support two you would need to buy a Printrbot Extrudrboard, another hotend, more wires, and another stepper motor. This would all run you more than $100 more to buy and be fairly difficult to get working reliably. The other option would to be to upgrade to RAMPS, which would cost about the same, but have more room for later upgrades. Either way, it will also limit your bed space and require major alterations to the x-carriage. I would only venture into these options if you are already used to and comfortable with working with consumer-oriented 3d printers such as reprap or even Solidoodle. The maintenance they require is a lot more than one would initially expect.
Unfortunately, for that price point, such a machine does not exist, and probably won't for at least a few more years.
One last note: Keep in mind that support material can be printed using the same material and extruder as the model. It can sometimes be tricky to remove, but often will peel away easily. Therefore, dual extruders are not a necessity in my opinion.
