At the bar I use a laptop (or rack mount a pc) with audio in to a Yamaha mixer and VGA to an audioauthority VGA to component scaler to feed the televisions. I use KJams software ($100) and subscribe to tricersoft and chartbuster ($99) which gives me approximately 70,000 songs to pick from. No physical media.

For mics use Shure ULXp4 wireless receivers (rack mount side by side 1u) and Shure SM58 wireless mics.

Behringer has some relatively inexpensive rack mount mixers. A mixer with effects is a must for the all important chorus reverb and karaoke echo effects.

Mixers with iPad control apps are becoming more common..

Use wireless keyboard to control kjams. Kjams also has a built in webserver for integration.