Hello all, 
 
I just bought Amplitube's Mesa Boogie package.... it's pretty awesome.  The only problem is that, after I insert it as a VST, I can hear the sound of the amp AND the unprocessed sound.  So, it's like the Mesa Boogie amp model and a clean guitar tone at the same time.  I never had this issue with Guitar Rig.  Any ideas?
 
EDITED:  the resolution was to go to the "cabinet" of whatever amp you're using and turn OFF the "DI" knob, which apparently is the clean, unprocessed signal.  

Its your audio interface. Open the control panel and select DAW tracking/ turn off input monitoring.
You are essentially hearing both the VST and the unprocessed signal.

I don't have that as an option in my interface's control panel....

Sure sounds like an input monitoring issue to me.
Every Soundcard now a day has some sort of way of using live monitoring, input monitoring.
Well this is great for some instances. but in the cases of using guitar sims, you end up hearing a blend of live monitoring and VST guitar sim.
Just search around in your hardware settings. look for input monitoring. turn it off.
 
The problem there lays in the routing. You shouldn't be hearing the clean signal from your  M Audio C 6000.
You should be hearing it within sonar using Input echo and the tracks Rec widget.

There is a way within amplitube to mix the direct signal. Maybe it's that?

Thanks for all the responses.  It turns out RSMCGUITAR was on the right track.  Apparently, on the cabinet's "page" (for lack of a better word), there's a "DI" knob at the bottom.  I never would have noticed that knob, never mind known to turn it the hell down to zero, but.... that's the resolution.  Thanks everyone.