using onboard sound with my Focusrite

Hi all
 
Strange question, I know...but I'd like to use my onboard soundcard (ASUS Realtek something) with Sonar.  Basically, I want to send the master bus out to the Realtek and the Focusrite at the same time, or with a simple switch between the two.  I'm using the Focusrite 2i4 with the ASIO driver.
 
I tried installing the ASIO4ALL driver, but then Sonar ghosted out the Focusrite, so I can't even select the Focusrite I/O at all.
 
Is this even possible?
 
Thanks!
 
 

Thanks.  I solved it another way - just disabled the Realtek altogether and plugged my speakers into the Focusrite.  I was running everything else (iTunes, etc) through the Realtek before, but now everything runs through the Focusrite and that does the trick for me.  I just wanted an easy way to use my 2.1 computer speakers as a reference for mixing.