EMC max step frequency

Hi!

I am planning on building a router using
ac-servo drives with step/direction inputs
(reprogrammable for +/-10v inputs for posible
future full servo system).
I would like to get about 40-50Khz.
What is the maximum pulse rate to expect
from emc, I am running a AMD K6 550Mhz,
is this enough or should I build a faster computer?

Running steppers, what would be the best choice
today EMC or mach1/2

Best Regards!

Lars Levin