Lower motor current translates into less torque available from the steppers, so potentially lower max speeds and acceleration. The only way to find out is by testing - run a series of tests involving faster and faster speeds, checking that the spindle always returns to the same point. Back off a bit from the fastest working speed to give a bit of leeway. Then ditto varying acceleration. In your case, you might look for higher acceleration at the expense of speed, as with fine work you seldom get up to full speed anyway. That's one reason why no-one can give you hard-and-fast numbers - not only do machines vary but so does the kind of work done.

Good luck!