I don't think I was clear enough in my original message -- no, I'm not
looking at any of the real bottom-of-the-barrel machines. Bottom I've
looked at seriously is the Northern Tool; now it turns out that
Electric Arc has what looks like a very nice machine that a local
welding shop is offering for under $500.

What's got me puzzled is the weird stuff that seems to happen down at
the far bottom -- and it looks like these things are screwy to the
point of not even being constant voltage.