I was given a MEC 650 press in 12 ga. I already had a 650 in 12 ga, so I converted it to 16ga. It can be done. I would not do it again and I will never change it back to 12 ga. There is to much fiddling around with adjustments to get it set up.
MEC sells conversion kits for several of their loaders. They may be a lot easier to use than what I did.
IMHO I would go Gauge specific with presses. I have seen many used MEC 12 and 20 ga very reasonably priced. I have never known of a used 16 ga. I have a feeling that you are looking at buying that one new. There are both progressive and single stage presses out there, shooting volume would determine which one to buy.
Curt