As an alternative to the advice given by dcumpian (who certainly knows his stuff

):
- Unsolo your Master Buss
- Ctrl + a (or ctrl + shift + a - they do exactly the same thing for this purpose)
- File > Export > Audio > Hardware Outputs
Select whatever options you want from the Export dialog box,
The above settings are typical for preparing a mix for mastering.
If you want to burn to CD, change the bit depth to 16 and select a Dithering algorithm
Note that the destination defaults to the setting in Presets > File > Folder Locations > Wave Files
The text box under Source Hardware Outputs might show more than one set of Hardware Outputs depending on how many are exposed/routed in Sonar. If this is the case, only select ONE of them.