I recommend a LabJack for your USB data acquisition. I've been using a LabJack U3-HV for a while now and like it very much. I especially like the way you can control it from any programming language you prefer on your system. I use Excel (visual basic) to perform the setup, run the logging, make real-time control decisions, and so on.
It has pretty good precision at low voltage, but you may still want to use an op-amp to boost the signal.
I believe the DATAQ devices can be a bit cheaper, but for me were also less flexible.
It has pretty good precision at low voltage, but you may still want to use an op-amp to boost the signal.
I believe the DATAQ devices can be a bit cheaper, but for me were also less flexible.