check out
www.weldingweb.com for some expert insight.
i am one seriously cheap bastard but dropped the coin for a Miller 140 and am happy i did so.
keep in mind that SS is, IIRC, typically done with Tig machines. in Mig you will have a different gas for SS (vs. mild steel) as well.
i'll tell you this much for sure: once you own a welder the whole world is a broken steel table leg.