Confirming PSU spec for steppers.

[JAZZCNC]

Ok the calcs you've done are close and correct in some ways but some of what you read I think you miss understood.? The 752s Manuel and 50-70% was referring to current not voltage. So you still need 57V but only 8-9A current.

That said has you know the voltage is what gives you the speed in a stepper so dropping to 48V means your only getting 85% of the speed you would at 57V. PLUS these motors will happly run at 70V thou I always run them at 65-68V to give a better margin for Back emf. So really at 48V your only getting 69% of the motors potential at 70V.?

Now in speed terms to the machine it can be dramatic in terms of the motors corner speed or point torque starts dropping away.
IE @48v then expect the corner speed less than 700rpm and @70v approx 1000rpm.
On a 5mm pitch screw then it makes the usable feed rate difference between @48=3500mm/min and @70v=5000mm/min.

Without knowing more about pitch and what you want to cut then hard to say best route to take.? .. BUT . If the voltage can provide the speed in combination with your screws to give the feed rates you need to cut what you want then it's not an issue really simple has that.!!

Remember high rapids mean pretty much nothing in real world cutting unless you intend to do lots of positional moves like drilling or have a massive long machine.? . . Mostly just bragging rights.!!

That said I prefer building my own supplies so obviously can build it to my exact needs so nearly always 65-68V using 75V drives simply because I can.! The amps just depends on how motors and number of them.
It's easy building a toroidal PSU and often cheaper plus safer for the drives has they handle back Emf much better and gives a nice consistent supply of power.

For me it would be "Build own to my exact needs" other wise if speeds/feeds it allows are OK use the 48V@12A and save the money.! Certainly wouldn't buy 2x68V@5a has could easily build for less than price one.!!!