The console has 2 main outs plus some others that are assignable.  It's a pity that these main outs don't  serve for playback Sonar...

There would be a huge latency from SONAR. There should be no need to monitor through the DAW, if I have read the docs correctly, the REAC connection to the PC is intended for audio capture only. Monitoring the mains (directly not the return from SONAR) would be similar to the near-zero latency monitor most interfaces provide.

scook
There would be a huge latency from SONAR. There should be no need to monitor through the DAW, if I have read the docs correctly, the REAC connection to the PC is intended for audio capture only. Monitoring the mains (directly not the return from SONAR) would be similar to the near-zero latency monitor most interfaces provide.

I understand.  Well, at least, the console seems to be a very good device to record live...

Yes that is the point of it, Most people use them in Churches and such and only want to capture the service then edit and re distribute as a stereo podcast or CD's. If your wishing to use it in a studio set up then you need the addition of the interface. REAC is a Roland thing that no one else uses so guess what, your stuck with a Roland interface. 
It's a very cools system used as intended for live performance. 
Those who wish otherwise purchase mixers that use common audio digital formats so that different brands can be intermixed. .