I run a Lincoln SP-175T. No problems, great capacity, great welds. I've run a few 10lb spools through it with no feed problems. For fab work, I would recomend no less than the 175A welders, Lincoln or Hobbart/Miller. It's a matter of prefference as to which one is "better" IMO.
Duty cycle is all relative. For someone doing fab work, the 20% I have is fine. I've hit the cutout once, and that was while welding my front spring hanger for my SAS together. It took me about 30 minutes to hit it on high power. For home fab work, I think that's enough. For professional use, it may not be. The lower the power setting you use, the longer you can go as well. I used 1/4" for my hanger and had a lot of welding to do on it. When I welded to the frame, which was about 1/8", I went for over an hour without hitting the cutout. I wanted a break before the welder did.
My biggest reason for choosing the Lincoln was that the consumables are available everywhere. I can buy contact tips at Home Depot or Lowes! That's real nice if I need one on a Sunday afternoon. Not that contact tips need replacing often, but it's nice to know I can get parts when I need them. I've only needed it once, for wire. I think they carry most of the consumables for Lincoln at HD. I have nothing bad to say about Miller welders though, good machines and worth the money.
I would also recomend getting gas. The wire then costs less and the welds are better. I run C25, but CO2 is cheaper and works well if you want to save some money.
For $500, you're probably looking at the Hobbart Handler 175. $578 at cyberweld. Get that and run flux till you come up with $100 or so to get a gas tank. It comes with everything you need to run gas except the tank. Even if it's a little more than you were looking to pay, nobody ever complained about having too much power available.
