I think Mach can either use PWM or Step/Direction for the spindle.
One thing might be worth looking at is getting 3 phase motors for your machines, single to 3 phase VFDs can be got often quite cheaply on eBay, think the most I paid for any of the ones I got was £45 and £60 for my 5HP ones for the Bridgeport. I have 3 phase so the ones I have are 3 in 3 out but some can be used single in 3 out with a bit of derating, a quick check of the manual of any you see will let you know if thats the case. Also eBay is a good place to pick up 3 phase motors as they go fairly cheap and once you have them you will get more for your single phase motors
Hood