Reply to Ableton Launchpad & Stand-Alone Mixer

So ive really started to want more flexibility in Djing...i still have an S4 and i use traktor when i play at friends parties but i got the ableton demo and ive been playing with it for about a month and I want to move over using the novation launchpad...so my question is;

Assuming in live i assign Audio 1 to Channel 1(on the mixer) and Audio 2 to Channel 2(on the mixer) could i not just then have tracks playing in live and mix them in the mixer? Unless im missing something here?

Also i realize I would need a sound card which i also need to decide on (along with a mixer choice too).