MaxNC Servo Upgrade

Hi group,

I have the MaxNC-15 Servo, (nothing more than a stepper with encoder
feedback).
I bought it to do a 1 tool production job and now that it is done, I would
like to make
it more useful. What I'm looking for is a bigger (ie: more torque) stepper
motor. It currently
has Pacific Scientific PowerMax II #P22NRXC-LDN-NS-80 motors.
Also I want to replace the cheap 1/10 hp AC/DC spindle motor with a 1/2 hp
Sherline
variable speed reversible motor. Their motor is run as AC with control thru
the software, but
no feedback as to the correct RPM.
Anyone know of a good replacement stepper motor? And can I replace the
spindle motor
without too much modification to the electronics?

I'm not an EE, I'm a CNC machinist/programmer and am used to having more
power (argh! argh!)
It is a "nice" little machine (after a few mods), but I'm shooting for a
"great" little machine.

Thanks for any help,
Don Panzer