I used servos on my mill/drill (RF31) and the last set is rated at 48V 1000 rpm and the first set was 110V 6500 rpm. I changed so I could have
1) MORE power
2) utilize the power of the motors within their voltage rating (geckos are limited to an actual about 70V power supply)
Now having said that, I like the servos as they are smoothm but it took some doing to get there. You will need encoders (steppers don't) and of course this entails more wiring.
Plan your system out. Get your servos first (and make sure the drivers you select will handle the required voltage) See item 2 above
Figure out what resolution encoders you will need if they don't come with the motor and how you will mount them! (Mine are mounted on the ball screws which would allow me to change the pulley sizes on the reduction unit without changing my setup parameters)
THEN after you have your servos and drives, worry about the power supply!
As to the source, I scrounged all the "surplus" sites I could find on the internet and that is where I found mine. The last ones are about 4" dia 6" long and weigh about 11@ ea!
If you want some additional info, let me know.