Inverter Drives

I'm looking at purchasing an Inverter drive for my milling machine. The
machine has a 3phase 3hp motor with a variable speed head. The spindle
speeds range from 80-4200 rpm.

I'm currently looking at two Teco drives - the FM50 and FM100. The basic
difference seems to be that the FM50 only goes up to 120hz, whereas the
FM100 goes to 400hz. Will I ever need/want to run the motor at >120hz?
Also, ultimately I want to control the rpm with Mach1/2 or EMC. Are there
any potential problems with either drive for doing this? Has anyone else
used either of these particular drives?

Thanks,

--C.S.