Since everyone else have praised midi controllers, I'll have to give it to synths. It depends on what your style of music is like, but I'd advise you to get a used synth. I recently bought a roland xp-60 and I'm loving it. The presets are ok, but when you get to programming, it gets hot. The keys are good and there are enough of octaves for a real keyboard player too (which I'm not). Of course you'll need more things like a mixer, compared to soft synths, but it doesn't need spicing up with compressors so bad either. There are loads of other models, that would be just as good, so pawn shops and music stores are the place to head.

The oxygen is a good tool too, if that is what you want, but go and check it before buying. The after touch is a bit weak and if you actually play with two hands, the octaves just aren't there. On the plus side, it's dirt cheap for what you get and it's got more knobs on it than the parliament. uhh, wait a minute, no it doesn't :cry: .