Scott, you can't ever have too much power out in your shop. I would not go with more than a 100amp sub with a 200amp main. However, a 100amp will be okay. You are going to need to trench some pretty heavy wire, but having a 100amp sub would be a great advantage!
You would be suprised how easy it would be to overload a 60 amp sub in a shop.
Jeff Sudmeier
"It's not the quality of the tool being used, it's the skills of the craftsman using the tool that really matter. Unfortunately, I don't have high quality in either"