This is probably a bit premature, but I'm thinking of fitting servos to my Fehlmann Picomax 50 CNC table. Originally it had massive Superior Electric steppers rated at 2.1Nm nominal torque.

I like the Teknic ClearPath integrated servos and I think their CPM-SDSK-3421S-RLN will do the trick - https://www.teknic.com/model-info/CPM-SDSK-3421S-RLN/

However, I like a bargain, so I've been wondering about buying used servos and drivers from eBay. The trouble is I know nothing about servos! Can anyone give me some basic guidance on what to look for and what to avoid?