Sonar 3x Pro audio mix output assignments question...

I'm using Sonar 3x pro and I have a question about
master audio output tracks assignment:
I use a Echo Audio AudioFire 12 audio interface
and also use a Focusrite Scarlett 2i4 on my computer.
I want to assign all my audio tracks outputs to the Firewire 12
outputs 1 and 2 BUT I would also like to assign them
to my Focusrite Scarlett outputs 1 and 2 too.
I could use an audio cable from firewire out1-2 to Scarlett in1-2
and listen a 'copy' of my mix on the Scarlett but I'd rather like
not to use any external cable but use software assignments..
Is-it possible in the Sonar 3x audio mix output assignments ?
Thanks.
J-Pierre

As Steve has said you cannot use 2 ASIO audio interfaces together. You have to switch to either WASAPI or WDM mode but this is not recommended for quality performance from your interfaces. You'll then be dealing with things like latency and timing offset issues. ASIO mode is important. 
There's nothing stopping you from trying it just for listening or if your working with 100% MIDI projects. But I do not recommend using anything but ASIO for Audio involving overdubs. 
 
Below is the test results from using different audio modes and looping the output of the interface back to input. It's pretty clear that only ASIO results in near perfect timing. 
 
 
 
Why may I ask are you desiring to use the extra outputs? 
If it is so you can have more than one set of monitors there are solutions for that.