Andrew;
I think the Komatsu PC-20 models can range anywhere from 2.5 to 3 tons machines. I don't know what you want to do with it but at that weight you will have to consider a truck and trailer that can haul that weight. I have a Takeuchi that I guess is really a "mini" in that it only weighs ~3500lbs. Much easier to move with car trailers and 1/2 ton trucks. Regardless of size I would look only for machines where you have servicing dealers nearby. Older/used machines will need odds and ends to bring up to snuff. My machine had 2100 hours when I bought it and it needed a solenoid, a hose, fluids, etc. right off the bat. A mini ex is a great tool. Good luck.
SimS