If you're looking for a tight control loop, your application sounds like a great application to prototype on MyRIO, which has a deterministic FPGA to build your control loop in.
If you don't need an FPGA, then the field is wide open, as controlling a servo and a few feedback signals can be solved by many different products (not just NI). Have you given any thought to using a PWM controlled servo motor? The PWM could be controlled by a counter either inside the FPGA or using a counter on any of of DAQ devices... that way you wouldn't need an analog output at all.
If you'll let us know a ton more about your particular application, then we can tailor a specific product.
-John Sullivan
Problem Solver
