I'd second the idea of the used laptop. You wouldn't need anything very up to date or powerful. If you had a Yamaha Softsynth installed with Van Basco's MidiPlayer you could display Karaoke Lyrics too! PLUS, you would, for very little more money than any of the other solutions offered, have yourself a nice laptop which you could use for lots of other things (like storing/display of your sheet music, cakewalk sequencing, etc., etc.). $500 would do the trick easily.