Here's a nice signal flow diagram for X3.
 
From: https://www.cakewalk.com/Documentation?product=SONAR%20X3&language=3&help=Mixing.07.html
 

it is worth routing all your busses to a final pre-master (or "sub master" if you prefer that term) bus.
That way you can add final tweaks to the entire mix given that the master bus does not have pro channel or fx sends.
 
If you are not intending to master in Sonar (provide a final product) then it is not essential for mixing to have a pre-master bus as the technical term for that would be "ears"
:)

BobF
Craig posted a link to a best practices document a few days ago.  I downloaded but failed to bookmark.  Maybe he'll repost if he stumbles across this.

Did anyone ever find this? I was searching through his recent posts but couldn't find anything.