PC loop control

My new rebuild project is to have PC closed loop servo control.
This is the system it was born with and I am used to.

It seems that apart from a very pricy setup EMC is the route to
follow.

My present servo drives were working when the 'mainframe' died,
They have a + - 10 V control. However I have some drives from another
project which could be used if that was a better idea. These are
step/direction.

What extra bits do I need to get the PC in the loop and where
can they be obtained.

Kib