By "drivers" not included on the card, do you mean simply supplying the step and direction signal externally and let the user handle all of the power?
Yes, I mean that the card would provide only step and direction signals without powering stepper motors.
Between the control card and each motor would be a seperate driver, something like this:http://www.geckodrive.com/g210x-p-51.html
Previous driver would make possible to use motors up to "7A / 80VDC", which is MUCH more than is possible with integrated drivers.
Oh course having separate drivers would also make the system more expensive... But still I would like to have this option for more "serious" applications.