Bedroom DJ Need Advice

If you prefer playing from a USB-device and need 4 channels, you're not looking for a controller. You need stand alone gear. If buy new gear it starts with the DJM-750Mk2 and the XDJ-700's and ends with the CDJ-2000/DJM-900 NXS2. If you can manage to bring your laptop running RB DJ, I'd suggest you look at the DDJ-1000, which has a stand-alone-mixer built in, similar to the DJM-750Mk2, and the price is quite similar too, but you get 2 decks similar to CDJ-2000NXS2 as a bonus. The drawback is that you need your computer connected if you want to use the built in decks. If you connect your 1200's and use real vinyl, the mixer will work just fine on it's own.

An XDJ-RX MK1 or MK2 would probably meet your needs too. You can connect two vinyl turntables and mix between a digital file (from USB stick) and vinyl easily, it's just a small switch on the faceplate of the unit. You WON'T however be able to mix four sources simultaneously. If you want to mix 4 decks simultaneously then follow Peter's advice above.

oh you posted in the wrong forum btw, this one is for features we'd like to see Pioneer introduce :)