MM STUDIO: 8 channels!
MM Fusion 4 channels, but two outputs! One for headphones, one for the external soundcard which goes in the hi - fi system! A timeline with which you can mix all before it goes out, like at all modern DAW's for dj's, but a bit different.
You don't need more channels as a dj, only for producing. Also Traktor has two or four channels. If you want to make a producer performance, then Ableton Live with the new controller would be good for you!