Try running the vocal track through an high pass filter and sweep until you find the frequency at which the pop loses energy. It should be somewhere between 100 and 300 hz. When you find the perfect spot, slap on a multiband compressor with an extreme setting to take care of excess of energy in that frequency range. That should help tame the unwanted low end rumble.

Anderton
If someone told me RX4 had a setting to wash your dishes and clean your laundry, I would probably believe them  

Won't fetch coffee though, even if you make it yourself

Split each offending plosive into a separate audio clip.
You can then apply a high-pass filter (non-destructively) to each of these plosive clips via Sonar's clip-based processing.  The energy of a plosive is typically going to be below 100Hz.
 
If you insert an FFT display, you'll see a large peak where the energy of the plosive is located.

I prefer splitting just before the plosive and applying a fade in. That way you can dial in the exact amount of plosive you want.

Anderton
I prefer splitting just before the plosive and applying a fade in. That way you can dial in the exact amount of plosive you want.

That'll work too...   
Got to love tools that are so flexible that there are multiple (good) solutions to a problem.

Anderton
I prefer splitting just before the plosive and applying a fade in. That way you can dial in the exact amount of plosive you want.

... and it's non-destructive - so if you edit fast and overdo at one point, you can easily back-off later ...

As luck would have it, I wrote an article in the Cakewalk blog about vocal tips using DSP. The plosive nuking trick is the first one in the article...check it out.

I just hand trim from the left of the offending pop until the P is still there but is now more of a p.

And when finished... send a copy of both the raw take/edited take to the singer and tell them "You need to work on your mic technique, as I spent [x amount of time] fixing this for you."

mettelus
And when finished... send a copy of both the raw take/edited take to the singer and tell them "You need to work on your mic technique, as I spent [x amount of time] fixing this for you."

Or if you're charging by the hour, say "Great stuff! Just keep doing what you're doing!"