I have an Einhell SGA 150 and it's suitable for what I do. I welded car sheets and some 5mm thick steel and worked well. It has automatic wire speed selector and fine tuning and works whits 0.6 / 0.8 mm wire. I have it for two years and no problems by now. I also did some alu work too.
I had an older Einhell 140 that worked well on the higher power levels,but was totally useless on thin metal below 1.5mm,as it would not feed wire evenly and used to leave blobs of weld floating on the surface.
Had the machine serviced, but never managed to get it to work better on lower settings,so I would not recommend one.
I'm working with an Einhell BT-GW150 MIG welder, and it is a pretty good machine for it's price. Power goes from 25 - 125A in 6 steps. Wire feed has it's own quirks sometimes but generally it works fine. For the price I can't be more satisfied. Machine is a newer (blue) line of Einhell.