Confirming PSU spec for steppers.

[Robin Hewitt]

In fact, taking that on board, I might shift my plans around a bit. I'll still finish up the PSU first because it's nearly finished anyway!

If you have already bought the toroidal I say go for it, something else could crock the project and fixing the PSU would only waste money.
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The problem with transformers is that when you rectify them to DC the voltage drops when you draw power. You can stuff capacitors in until the cows come home but if you don't rectify all 3 phases, the volts will sag.
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Similarly the volts will soar if you get a mains surge so you really need to protect your drivers if they don't protect themselves. Fortunately protection is cheap and easy if you use a crowbar circuit and wire a diac to blow a fuse on the DC side if you go over volts. A crowbar circuit is cheap and simple. Leave yourself a note by the fuse because it is very easy to forget it is there even after it just saved you hundreds of pounds