Mastering question perhaps?

Do you trust your monitoring? Does the bass sound OK when you export, but too loud in other systems?
How does your projects low end look in a frequency analyser compared to a commercial CD of your liking? Stereo/mono is not the answer.
Basicly, if the bass sounds disturbingly loud, it most likely is too loud.

One trap with the low end could be leaving too much below 50 Hz, which is mostly muddy mumble. The punchy, defined bass is higher than that. If you haven't tried yet, try putting a HP filter at 45-50 Hz.

It sounds like a monitoring problem in your room.  Mixing is an experience thing, and not just with the sounds on tape etc.  It is learning from experience how your system translates to other systems and in general.  For example, the sound system in my jeep is pretty good, but on some songs the bass just blooms.  Other songs it just disappears.  There was a thread about this kind of problem a few weeks ago, and stems from the cut off frequency in cars and the natural resonances.

Frequency analyzers give a 2 D readout of the song (or room), showing where the energy is.  I imagine you have a big problem in your room where certain bass frequencies disappear.  You mix accordingly, but then they are too loud on other systems.  You can see this in the read out.  Other than knowing the problem is there, it ain't going to help you much.  I suppose you could find the frequency to cut, but w/o hearing it is hard to find the slope, etc.   But it can help you "fix" your room with bass traps and other goodies.

@

Would of been nice if you posted a link....

In my experience, it's not the lwo bass that causes problems, it's the low mids that can easily be overcooked and cause mud build up.

In answer to one of the OP's questions - no, don't bounce your bass track down to stereo, leave it as mono.

Thanks guys. Very inspirational info that inspired me to dig deeper and use your suggestions. I figured out that it is my monitoring system. All levels may sound good in Sonar but the end result is always too boomy at the bass. Turns out that all the levels were too loud but the bass is the easiest to identify because of the boominess external sound systems will play back. I decreased all my track levels by about -4.0 to -6.0db. The final out levels were maxed at -12.0db in Sonar. It sounded very good if I cranked up my monitoring system. But I also know that the exported project will sound very low and playback reflected this upon listening on an external sound system. What I did afterwords was to import the final project wave as a new project and then plug in boost 11. I boosted the project up by 6db and the output was set to -2.0db to -3.0db. THAT did it!!

Now the bass and all the levels are very listen-able on all my external sound systems. I like to always rate my project based on a flat response at the external sound system. NO EQ!! Now all that's left is for the listener to adjust to their liking. I succeeded!