MIG Welders: What to buy?!

Ignore duty cycle. Hobbyists will almost never weld enough to have that be a concern. I second the Lincoln 135 recommendations and I have one for small portable jobs. Also, spend the the extra money for a gas setup - skip the flux core wire. All automotive welding is considered light fabrication. There is nothing you'll ever build for a car that requires any steel thicker then 1/8" - if what you're building is properly designed.