Hey Soulphinger,
Good question and right up my alley 🙂 .
I have an MC6000 too. I used to have two American DJ CDI500s as regular CD-players hooked up for back-up and CD-playing capacity. I traded them in for two DN-S1200s that I can also use as controllers for decks 3 and 4. I have a MacBook Pro with all my tracks and settings on an external SSD with a backup on external HD. I have a Dell laptop as backup with a very stripped Win 7. Obviously I have iPhone and iPad with me and usually I will carry my Numark iDJ Pro as a backup controller. And a cheaper Sennheiser headphone and extra mic.
I have active speakers, so if one fails I can probably make it work with just one (or three depending on the room) and the sub.
I have plenty of other gear, but don’t bring it all to one gig.
Greetinx.