Hey,
If you have an MPC, the only thing you'll need are a pair of speakers and some sound sources, like sample cd's or a cd player/turntable.
You won't NEED to have another controller, but it sure makes things a lot easier if you want to play in musical notes.
'Top of the line' sounds like what the salesman told your dad before he sold him the keyboard...what model is it? The current big-boy from Yamaha is the Motif, they run about $1500. As long as it has MIDI ports on the back of it, you should be ok.
Take care,
Nick