Hi Matt.
My name’s Kyle and I’m an 18 year old university student near London, Ontario (Canada). I’m going into my second year of university to study astrophysics. I was the tech kid too.
I can’t answer your question about doing live mashups as it’s never appealed to me.
However, if I were you, I’d just use Ableton. Mashups in a club setting are very, very rudimentary at best – I use Traktor because I just do mixing when DJing. Ableton’s extremely flexible, but Traktor’s far more simplistic.
I’m not sure what you mean by requiring a mixer with XLR out, as you could just record mashups in advance and play them from Ableton/Traktor/VDJ/etc. Personally, that’d be my choice because again, I just mix. Using a launchpad and doing mashups and finger drumming live only has the “wow” effect in parties and on YouTube, reason being that in a club people are just dancing really. It’s up to you, kind of like how some DJs manually beatmatch just because it adds challenge and satisfaction.
As for picking a controller, if you do it live, you’re gonna need a 4-deck controller, or you won’t be able to mix out in time. If you prerecord mashups, you could get an S2 or something a bit cheaper. Save up if you can – I bought a Hercules DJ MK4 and now it’s a moderately-priced paperweight.
Welcome to the wonderful world of DJing, anyways!