I think it depends a bit on what type of control software you want to use, Mach3, EMC2 or some propriatary for the particular controler....
The DSPMC from Vital Systems is a motion controler at the end of a ethernet cable - $995. As far as I know the DSPMC does not yet support step and direction but since you mentions PID etc in your post I guess you want to run servos even though you posted in the Stepper motor and drives category.
There's also the motion control cards from Dynomotion although I believe they are USB and not ethernet. It outputs step and direction by default but can be converted to analog with the add-on card (KAnalog).
MESA has range of cards as well, I believe the 5I20 (and perhaps others) are supported by EMC2.
Then of course there are some products from Galil (and other "industrial" suppliers) but I don't know enough about them to say more.