Hi Richard

I am unable to comment on Routoutcnc as never used it.

To modernise the Triac you may be able to use the existing stepper boards with a different control system so will need a minimum of items to do the conversion.

If you have to replace the steppers and driver boards std units are not so expensive, servos will cost much more and may not be viable for a home workshop, depends of course on your use.

Steppers are available with feedback and have matching controllers, this set-up would be a mid point cost between the 2 other methods suggested.

Probably the existing spindle controller can be connected into the new system so very little or no expense.

The PSU will no doubt be suitable for a conversion so no cost to add, just connections to bring the various voltages into the new system.

So seems you may only need a break-out board to distribute the OS control wires to the new system components.

Emgee