erezg,
We have had many customers put together systems that do very similar things. We do have very fast and accurate DAQ cards, but we also have a series of cards that are made for Motion (for more information:
http://www.ni.com/motion/) and have ports for Digital I/O. That site is probably your best resource for getting more information. If you tell me a little more about your application - I know you have servo motors and are reading a diode signal, how many motors? what kind of resolution would you need? etc. - I'd be glad to recommend a few cards. Let me know if you have any questions, or would like any formal quotes sent to you concerning our cards. Thank you!
-Allison S.
Applications Engineer, NIC
-Allison S.
Calibration Services
Product Support Engineer