What are your pan laws set to in Sonar? The default is 0 dB center, but almost every other DAW in the world defaults to -3 Center, Sin/Cos Taper. You can find this in the Preferences Menu. This may affect the way you hear the relationship between the center and the sides and can really affect gain staging.
With Sonar's default it doesn't take too many tracks running fairly hot for me to have my track gain and faders all at 0 and be overloading my Master bus with its gain and faders at 0. Setting to -3 makes this instantly more manageable.
I would recommend changing the settings in your Normal template so that every project will default to -3 for the pan laws.
Peace,
Tunes