Is real-time signal processing possible under Windows?
if you need to keep jitter (assuming that's what you mean by "wiggle" :) down to &lt;1ms I'd say forget Windows.  Does the absolute latency from input to output matter, or is it just the jitter?

You might manage it some of the time, but guaranteeing it is unlikely.  What's the penalty for failing to meet the deadline?  Will it blow up speakers?  Drive a robot arm too hard against an end-stop?  Or something more benign?

The fact that your output is USB is also not likely to help in the jitter stakes as there's lots of extra OS interaction there, and the topology of the bus will also hinder your potential latency - if your output is at the end of a string of a few hubs, for example.