A karaokee player setup generally is playing Cd-G which is cd with graphics. That way you can hook up a video monitor and see the bouncing ball. The karaokee machine setups usually have a place for a couple mics, generally ballanced or unballanced 1/4 connections ( yuck!), and controlls, and a built in speaker... The better units may have audio out, for hooking up to a seperate amp, or at least speaker lvel out for attaching other speakers... May have better mic channels.. perhaps even ballanced xlr inputs.. though I've not seen a unit with phantom power.. I think the more you pay, the better mixing controls you get... graphic/parametric eq, better sweeps, presence or lack of a mic pre-amp, better effects section. I've sene some American DJ equipment even have key correction / pitch bending / shifting, and a vocal remover for playing a regular cd.. which just more or less just carves the 'middle' out...
You can find them from 19$ and up at walmart.. or if you want a dj or pro level job, hit a place like musicians friend ont he web, or Sam Ash.. they both have DJ sections.
Soundguy