This was covered in my Advanced Workshop video (ahem), but forget about using the Sonitus compressor as a bus limiter. The best limiter that comes free with Sonar is the Sonitus Multiband compressor. A multiband compressor is
much better on program material than a standard compressor, as there are less artifacts (e.g., you don't have issues like the kick compressing the highs).
To use it, on the Multiband Compressor UI, click the Common tab and click Limit. Raise the output above 0.0 until you get the desired amount of limiting (within reason, of course). Multiband will clamp the output so it stays below 0.0dB.
However, if you plan to turn your track over to a mastering engineer, add NO processing to the master bus. When people do that to me, I act like the picky person in the restaurant who sends the steak back, and ask for a version with the bus plug-ins disabled.