It is probably a matter of opinion here but my approach, providing the machine is already driven using bipolar stepper motors, would be to replace the existing controller with a cheap, Chinese, multi axis board similar to one I used here for an old Boxford mill
http://www.cooperman.talktalk.net/files/14.htm (In your case there would be no need to remove the machine from it's cabinet etc). Many parts such as the PSU, spindle speed controller etc will be reusable.
This then makes the machine 100% compatible with Mach3 operation. There is quite a lot of work involved but it is not an expensive option but check that the stepper motors can be operated in bipolar mode (that they have 4, 6 or 8 wires). If the motors are 5 wire unipolar steppers or servo/encoder types then there would be much more expense involved and it may not be an economic project to complete on a budget.
Tweakie.