The question comes in with who will be running the system? If you don't have a KJ to run the system - someone with experience with professional sound and the ability to make an evening entertaining for the singers you might be better off with a karaoke jukebox where you pay for each song.
There's nothing worse than a karaoke setup with a dozen discs lying out on a table w/ a Vocopro all in one cabinet beside it.
To accurately answer your question though, we need a little more information - is this in a bar, a side area, open with the bowling alley, etc?
More information on the layout, how large a space, frequency of karaoke, size of the crowds, layout of the space, etc are all important things to consider. If you do karaoke once a week would you be better off hiring it done? There are lots of questions that need to be answered to accurately answer your question. And even then it really needs a site survey to accurately determine what would be 'best'.
As for equipment - it's best to buy seperate components. Depending on the choices you make, some equipment might be better choices than others. Can you get buy with a VocoPro 7000 Mixer? Sure, but there are better options (Mackie's DFX/CFX, Onyx lines, similar Behringer offerings, etc). Are powered speakers or seperate amps/speakers best for your establishment? Depends on a number of things.
My recommendation is to talk with an audio professional about your setup- preferrably one that doesn't have a vested interest in selling you something - even if you have to pay for it. Once you have an idea of what you want/need, start shopping, ask for specific recommendations on equipment, etc.
Depending on where you're located one of the more knowledgeable members might even be able to help out but again it depends on where you're located. Unless you're in Anchorage, Alaska or Pensacola, Florida and looking for someone that's relatively new to this as well it's not going to be me.
