The way my systems is currently set up, my record volume level and monitor level are the same.  In order to change the monitor level for my singer, I am by default also changing the record level.  I have read that the (post) fader level is independent of the record level, and thay I could change the monitor level with the fader, but this is not the case (I am probably misunderstanding this).  When I change the fader level, the record level also changes.
 
My sound card is an M-Audio Fast Track Ultra.  I have played with the monitor mixing in it's software, but in playing with it it has no effect other than to change the overall monitor level.

I would appreciate any help getting the levels separate.

Ha! ...you need a headphone mix...check out my last post...might help you out...

http://forum.cakewalk.com/tm.aspx?m=2774148

sonar doesnt control any of your rec.input.
your interface controls the record signal(you fastrack
the key here is to either turn down the music to balance the all around levels.
you can control the monitor recording level through sonars fader.
but it wont have any effect on the signal.
fast track controls you audio signal plain and simple.

imagine that sonar is just a daw waiting for a signal,thats all.
it has no control over the gain you send in.thats why its important to make sure when recording you have a good signal to noise ratio

In the analog days this was easy.  It is more convoluted in the digital world.  There are two mixers, many times.  The SONAR mixer and the interface's mixer.

I'm not familiar w/ the maudio unit (or any maudio unit) but SONAR will let you assign each track to a send(s).  YOu then route that send to a separate bus, and route that bus not to the master bus but a hardware output.  The send should be prefader, so the send knob controls the volume (just like the track fader does for the master bus). 

On the SONAR mixer there are three expandable panels: Tracks, buses, and hardware outputs.  If the maudio has separate outputs, that should show up in the SONAR's 3rd panel.  Assign the monitor bus to that.  Then you need to make sure that the maudio software mixer is set up to send two separate stereo signals to the two outputs.  This may be where your problem lay.

@

Wooopos ...my bad...I think I might have led you wrong..I didn't read your post quite thoroughly enough...Chuck is right...

My method is to add a bus and send the current track that you're recording to it. I call my bus Live Monitor. You can add Breverb on that bus as well. More volume on that bus or lower volume on your other stuff either way you can have the live recording track take front stage and the rest can be set back to a level that works.

Thanks for the help guys, it worked and here is what I did. I de-linked the outputs in the Maudio monitor mixer, then I created a send from the live audio channel to a bus "Live Monitoring. It took me a few minutes to realize I add to unable echo thru on the live channel.  
 
Thanks again!