You NEED to use an UNregulated supply. Motors and motor drivers draw massive current when a coil turns on and release large spikes when the coil is released. A poor little semiconductor trying to keep that regulated is just going to have a nervous breakdown!

I'm a little weird on this, but I really like car batteries with chargers as power supplies. You put them in a battery box, and NEVER overcharge them (cheap intelligent chargers are everywhere) so they are pretty safe, especially in a shop or garage. And then you can't possible not have enough current handy... Cold cranking amps right? The only trick is you have to stack them for 24, 36, 48 volts and that means the chargers have to play nice when stacked (not a given) or you have to find a charger for that voltage of battery which can be done, but isn't as cheap. It's a bit of a pain, but there can be no finer power supply!

Other than that, some people have been able to stack PC power supplies... that's scary... but cheap.

Let us know what you find for a supply? I'd like to collect some good recommendations for the page at:
techref.massmind.org/techref/io/stepper/power.htm