What kind of paint works best on MDF board?

If you're spraying lacquer you'll need to use a vinyl sealer. If you're spraying paint you'll need to use a primer. In either case you will have to sand between coats and after the final coat has cured for at least a couple of weeks you'll have sand the finish as smooth as a babies bottom and then rub out the finish with rubbing compounds to obtain a mirror like professional high gloss finish.

Thanks a lot for the helpful advice guys I really appreciate it. I didn't realize how many layers of primer and paint you need to make it come out good, but now I do and it will!!! THanks again,
Kris

Gloss spray paint has worked the best for me

I prefer whatever kind that I can get my wife to put on....

Makes me glad that I didn't build my own speakers if this is what's involved in just the paint job!