I am wondering what the deal is with MKI's. They are supported, right? And they are pretty historic pieces, I'd say. But are they functional? Is it worth buying an MKI because it's not only an empeg, but a rare historic empeg?

If it fully functional, then hell yeah! Can you get a 303 face for it (since it has the handle that all the 303face fans want)? Can you hijack it? I mean, for $500, why not get the MKI. It's cheaper than the others, you'd own some history, and you'd have a very rare piece that the "new school" MKIIx owners wouldn't.