I'm assuming you would be using a computer, yeah? If so, why not just get a USB midi controller? MIDI controllers don't contain sound though, you must process your sound through your computer and trigger it with the keys/knobs/faders on the controller. If you want a cheap synthesizer that can also be a MIDI controller, I think that's a pretty standard feature these days but the microKORG is a solid buy though it's out of your price range by a bit. It's still quite a cheap synth and great quality for the price. Check out M-Audio for some cheap options on controllers but I gotta tell you, I think M-Audio stuff is kinda cheaply made. If you spent a little more you could get a real nice Akai MPK25 or something. Also depends how many keys you want, 25s are going to be cheaper than 49s or full size keyboards.