If you just stick the NS-2 in front or in the loop, you aren't really using its full noise-reducing powers. That pedal actually has a loop of its own, and ideally you want all your distortion stages inside the pedal's loop.
Run it
guitar -> tuner -> NS-2 input
NS-2 loop send -> [other pedals] -> amp
amp effects loop send -> NS-2 loop return
NS-2 output -> amp effects loop return
If you're using a lot of gain, this will work better than using a single gate in front or in the loop, and should be better (or at least cheaper) than using two gates. The idea is that the gate is controlled by your totally clean signal up front, but opens and closes after all the distortion has been added.