Adagio4639
Ok..at the risk of sounding really dumb, I'm going to ask a question. But first I should say that I've been using Pro-tools for years. I have two Digi 002 mixers
FWIW, The Digi 002 is an audio interface (provides I/O).
Running Sonar, you have a wide choice of audio interfaces.
If the audio interface provides low round-trip latency, you can effectively use it (and your DAW) as a digital mixer.
Many current generation audio interfaces provide I/O... along with full routing, DSP-FX processing (EQ, Dynamics, Ambience), and external control via iPAD. This certainly blurs the line between audio interface and digital mixer.