Navigation volume problem
 

I own a 2007 H3x, and the volume is very low, using the original Monsoon Radio/Navigation pkg. (purchased the H3 used about a month ago)
I have tried raising and lowering the radio volume, and the radio volume works fine.
I have also tried raising and lowering the Voice Volume control via the Nav Options to no avail.
Short of taking it to a GM dealer, any suggestions?
Thank you in advance.