hey there, currently selling both of my sc2000s, the left sc2000 needs a mild repair on the filter knob (which does not effect this in any way, as you use your filter from your mixer), this is compatible with 90% of DJ software and yes, these do act as expansion using to a 4 channel controller... meaning you don't need to use deck select. treat these as an alternative for CDJ's without breaking the bank and simply plug and play.