Just get a power supply that has the voltage you need. You can get lots of different voltages. In case of using batteries, it's basically a matter of adding more cells - a Tesla operates at about 350V off batteries, for example.
The stepping I achieved through use of timer interrupts and direct port calls as functions like digitalWrite() are way too slow for that.
I created one timer that interrupted at 122 Hz calling a function to calculate the stepping speed (i.e. the period of each step), that's often enough for smooth acceleration.
It set a second timer interrupt for the actual stepping - to speed it up two separate interrupts for the two directions, no checking for direction in the ISR that did the stepping.
A third timer interrupt handled the updates of the 8-segment display and the blinking of the red/green LED. Normally one would do this in loop() but the other processes were such that loop() did not get enough time to run...
This was all running on an ATtiny84a. No pins left for a crystal; no space on the board for it or a larger MCU anyway, so I was limited to 8 MHz.
Over the Christmas break I gotten intimate with the Attiny412, I would definitely use one of the 0 or 1 series now. More functionality in the timers; more efficient PORT operations, 20 MHz internal clock. That'd have made my life a lot easier getting to that kind of ridiculous pulse rates, 200k steps per seconds with acceleration seems possible on those chips
The stepper controller that I had for that project was outright awesome. At low speed you could NOT hear the stepper running, at all. It was dead silent. At higher speeds it started to make some noise, mostly due to friction in the bearings and minor imbalance in the rotor and so. A big difference compared to our 3D printers which are basically playing music on their steppers as they operate...