pallen:
You mentioned that you were switching to USB to save $$. Be careful, I have looked at the specs of the 6008/6009 and I am not too impressed with the analog inputs, they have an input impedance of only a few hundred kohm. Some people have ran into problems saying their measurments were innaccurate- it turns out that the analog inputs were loading down their circuitry. No counter/timer support and software timed analog output too on the 09, I believe.
You may want to look over the specs of the USB devices before commiting to them. Granted I have never used one, but have heard other people issues and some have had to go back to traditional cards (PCI, PCMCIA)