If you have the Nav there is a reprogram relative the audio level of the radio.
The Nav radio gives up a little on the audio compared to the non Nav.
The regular Bose system (not Nav) has a lot more adjustability and function choices. They both are not what you would expect of Bose though.
Low volume on Nav radios:
Now, there is an update for Navigation stereo’s that suffer from low volume, this fix can be found in TIS version 2.75 and later, have the dealer install the latest software for the fix. If you turn the volume all the way up and the sound level does not reach an uncomfortable level for a reasonable and prudent adult person, now if you're a real head-banger then it may never reach that level.
What you should do if you are the owner of a 2007 Tahoe with Navigation is during your next stop at the Chevy dealer have the service advisor write a repair order up for "low stereo volume", ask them to make certain that your vehicle has TIS version 2.75 or later and also check for any other software updates that may be available, these are covered under warranty if you tell them a symptom that you have that corresponds to an update.