Any 4-deck controller advice?

Numark Mixtrack Quad is always a good call, cost-effective, reliable and compatible. But it really all depends on your budget and the specs you find most important. Identify which features are most important for you and cross-reference them with what’s available in the market then you should land yourself with exactly what you’re looking for!

I had a guy over at my place a few weeks ago who had a go at my MCX8000 and DDJ-SX, both 4-channel controllers.

4-channel control is the absolute minimum to be working 4 decks in a serious fashion.

Yet, this guy was having a bit of a struggle (although he did great from my point of view) juggling the deck choice buttons, he would sometimes not have switched before moving the jogs (which can be very disturbing if the current deck is playing over the PA.

I have once played with an option consisting of a Denon MC-6000 (a mk2 would do as well), complemented by two Denon DN-SC2000 which are effectively the deck part of the MC6000. That way you’d have 4 actual control surfaces, all hooked up to the mixer part of the MC6000.

http://www.digitaldjtips.com/search/dn-sc2000/ is a post that has a picture showing this setup next to a DDJ-SX and you can tell it’s only marginally wider.