it would be possible to do it with a 2 chan, but the problem is it will be layered on top of one of your other decks. just like you can mix with 4 decks on 2 channels, but that means you have 2 decks playing on each channel with only the 1 volume control. so you can do it, but practically speaking, its not very useful. much better off to have 4 channels for full control of the 2 main decks and 2 sample decks seperately. Im pretty sure theres a way to mix with 2 channels internal and 2 external. you just have to route them all external, but assign midi control to the volume of the 2 internal decks you want to control. That could be an option in the meantime. Then again, not super practical either… lol
so it is possible to do, but your much better off with a 4 chan mixer or controller.