I've been running a 650VA toroidal supply without any surge protector and haven't had a breaker trip yet, and that's with a standard B curve MCB and a couple of years of use. The other thing is that you don't need massive amounts of capacitor smoothing in this application as the stepper drivers are very tolerant of ripple. I have a nominal 68V supply and when I checked with an oscilloscope (and with the motors working) I see a few volts of ripple and it doesn't make a scrap of difference to performance. Well, theoretically it might but if you are that close to the limit, then you are really pushing your luck anyway!