Traktor 2 & DJM 700/800

@Mr P > The CD and Line inputs are pretty much the same. The CD inputs are designed for using CDJ players and such, but still supports Line Input devices. Meanwhile the Line inputs still support CDJ's and other Line Input devices. You should be fine using either the CD or Line inputs on the mixers. But if you have the 800 with the Digital Inputs, use them instead. :)

One thing is for sure though, never use the Phono input for any Line Input device/CDJ!!!! 

if you had a major problem with software you couldn't swicth smoothly to a cd only on channel 1 because the others are phono inputs... thats why i cant understand the logic in the design... maybe im just looking at it from a worse possible senerio.. i know you could prob unplug cables etc or reboot ... its correct on the nexus....  

@Mr P > What do you mean you couldn't switch smoothly to a CD only on channel 1?

If you're using software you should still be using a controller or a CDJ with the DJM-800 and DJM-700. Therefore the controller/CDJ should be connected by a Digital cable or RCA cables to the mixer. The channel should be set to CD on the mixer. Then if you have any problems with the software, you can pop a CD into the CDJ and it will continue to play through the mixer like normal. You wouldn't need to change the channel source or anything.

The DJM-900 capable of that because it has a built in sound card and can support each option on all 4 channels. ;)

yeah sorry , just dont understand the need for all the phono inputs...

lol no worries. There are at least 2 phono inputs because there are DJ's who play with vinyl and for those who use Serato with timecode vinyl. They need the phono inputs. ;)