Hi Matt,
Have you looked into buying some second hand Yaskawa servos. They can be had for around the same price of a new stepper set up and are closed loop control.
Look for the ones with a "P" in the serial number for pulse positioning ( what most of us use with Mach3 or EMC) and an "A" for 200 volt. "B" in the serial number would be 100 volt and "S" would be speed controlled which (I think) Mach3 can't do.
So...
If you had a servo motor SGMPH-01A1E4C then the P in it means it is for positional use, the 01 means it is 100 watts, the A means its 200 volts and the rest can be found in the manuals which denotes whether its a special, the shaft size, or some other manufacturer attachment.
The only thing you need to do is to match the drive with the motor or they won't work. There are a plethora of them on ebay and 1 set up shouldn't set you back more than $130-$150 for a good motor and drive. I have picked up 400 watt set ups for $80. You just need to look around and with your background the programming of the drives would be a cinch to get them set up to do work.
Richard.
The motors do 3000 revs tops so you have a great latitude to work with.