I think that depends on which output you have listed for Windows 7 which I just been through. If you have the speaker icon (for sound mixers of Windows) on your right hand taskbar then you change which output you are going to use there. Only two outputs can you use (left and right say) at one time. Then if you change it there, then you check the box on the output in Sonar, since I do not use ADAT as of yet, I only have to mark either Analog 1 & 2 output (in Windows it is the speaker graphics in playback), or Analog 3 & 4 in Windows and also Sonar which is the headphone graphics in the Playback section in the mixer section of Windows 7. Right click on the speaker icon on the taskbar or get up Control Panel - Sound, game controllers whatever in Control Panel and go through that to see what you have marked as for Recording and Playback (also Sounds there and Communications tabs) and if you change what input you want to record with or output you want to hear with, then both Windows 7 and Sonar has to agree, or you get no sound at all I think.
In XP it seems to be easier because you could read it better, but still you can read it in Windows 7, just those stupid graphics symbols also, as Windows 7 gives you all the inputs and outputs you can have and you can check all of them, but still in Sonar 7 as far as I know, you can only have two (left and right say) for any output as in stereo output which would be like Windows Media Player - playing a wave or *.mp3 file with that.
Otherwise I think perhaps (but since I have not used all outputs or inputs) that in Sonar 7 you would need the normal template and have the Master submix along with perhaps other buses below the tracks, but only Master bus is needed to route all tracks to the master on output which means that to me the inputs could be changed to whatever to record, all tracks inputs go to the Master bus for output which means in the end that the output is still only - say stereo (left and right) and the VU meters on top reflect the Master Bus output that goes to the output in have marked in Sonar 7 to use and also in Windows 7. In my case I am using the Analog 3 & 4 outputs and timing master in Sonar 7 but use the Analog 1 & 2 inputs to record through as the timing master. If I were using also the ADATs or SPDIF whatever then I would have to change the inputs in Window if not all checked and also in the Driver section of Audio menu item in Options to use whichever one at a time (sterero AdAT 1 & 2 or 3&4, or 5&6 or 7&8).
Since I am always using analog 3 & 4 output on my unit and in Sonar I never have to check Windows 7 because that is also marked there for playback, so checking Windows I am not sure if changing it just in Sonar. Perhaps just to make sure with the Windows OS stuff in Windows for the sound mixer. ??
Your outputs are what controls the VU meter in Sonar - in my case either it is directly the analog 3 & 4 output since I use those, or the Master Bus which also goes to the analog 3 & 4 outputs. I think if I were using two other outputs I have to mark those in Windows 7 and also Sonar with a check mark in Drivers of the Audio menu item of Options but only two at one time, so that is why a Master Bus is used to go to the outputs 2 which are being used.