yeah man, send the audio output through the kaoss pad and use it to make your mpc beats sound cool...
or you could plug it right before your inputs and sample through it.... like send your turntable through the kaoss pad and than into the mpc so you could add effects to your records or what ever.
I think the best way is to connect one of the individual Outputs (1-4) with the Kaoss pad, this way you can send one (or more) specific sample/track to the kaoss. So you don't affect the whole mix, only the samples you want to.