what is the least expensive welder i can get away with ?

I have a northern tool 125 (actually on my second as the first wouldn't feed wire, they shipped me another with no problems). I'm getting my money out of it and have done alot of welding in the last week and haven't over temp it. But I too wish I had bought a Miller or Hobart. I only bought the knock off for doing sheet metal as we have a Lincoln 220v at work.