The Lincoln AC 225 (DC125) was a steal at that price which is why it is already gone. The value is more like $250 even used.
For a hobbyist homeowner it is hard to beat a Lincoln AC225 (DC125), Miller Thunderbolt AC225 (DC150), or a Hobart Stickmate AC225 (DC160). While specs say that the Miller and Hobart have more DC amps, the Lincoln performs almost similary. In my opinion, the only real advantage of the Miller or Hobart is infinitely adjust amp settings (The Lincoln is tapped every 10-15 amps). Any of these welders can be powered off of 10 gauge wire and are light enough to move them around semi-easily. I previously had a Lincoln AC225 Only (NO DC) and since purchased a used Miller Thunderbolt AC225 (DC150). Comparing the two welders: The Lincoln was stronger on AC compared to the Miller on AC (both fed on same supply circuit) and the cabinet and cooling fan were made much better on the lincoln too. I only kept the Miller because it had DC. Had my Lincoln had DC, then the choice on which to keep would not have been easy.
The Lincoln Idealarc is an even better welder and some would argue one of the best transformer based welders of all time. That said, it is not ideally suited for a homeowner hobbyist unless you have a nice shop. The thing is immensely heavy and will not roll around that easily. Also, the power requirements are immense. I would not run off of less than 6 gauge wire as they can easily pull 70-90 amps depending on whether or not you have the power save capacitors and they have impressive duty cycle too so no skimping on power feed. Great welder for the serious user though if you have the shop and the proper electric to feed it.
As for buying used: I would only buy any of these welders used as a tranformer based welder will last forever. If it works when you buy it it will be working for your grandkids as there is so little to break.