Why dual transformers.? Don't see the point just adding expense for no gain. I've built many many PSU's and never had one faulty yet and that's running upto 5 motors.

I'd also just buy regulated linear 24Vdc supply it's cheaper. Doesn't make any difference just for powering switches or Boards etc and actually better for electronics because don't like flutating power.

You'd get away with 500Va but 625Va will give little spare current but you might get fuse tripping with inrush in which case just use D rated MCB.
Voltage then I'd aim to run steppers around 65-70Vdc. So you'll need to check your mains input but roughly 2 x 24Vac for series wired or 2 x 48 for parallel wired.