@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!!!!