sub issues

That amp does not have a subsonic filter, and you need one for your Solobaric.  Even though you are running at less than max power, at about 26Hz in your vented system the loudspeaker will be completely unloaded and can be driven to its mechanical limits.  This makes it easy to "fry."  I recomend installaing a stand-alone subsonic filter.  Harrison Labs makes one I've used in the past and set to 30Hz will protect your woofer.

Clipping is what happens when an amplifier is driven too hard and involves compressing the peaks of the output sine wave (it shows up as a near-square wave on an ascilloscope, and is called clipping since it appears that the sine waves have been clipped off.)  It can be detected by ear as a "shrillness" or "distortion" of a pure tone. 

Here's what I suggest for your setup.  You will need 1) hearing protection, and 2) a CD with a test tone on it at about 60 Hz.  Also, I suggest setting the low-pass crossover on your amp up to about 80 Hz.

First, turn the bass boost off (and leave it off) and turn the gain on your amp all the way down (counter clockwise.)  Next, set your head unit volume down and play the test tone.  Wearing your hearing protection, slowly turn the head unit volume up and listen to your sub output until you can detect that the tone seems to have changed (it should seem to get a little "sharp" or shift upward in frequency.)  This is being caused by clipping in your head unit or your factory sub amp.  Turn the volume down until the tone returns to normal.  NOTE THIS SETTING.  This is the HIGHEST you can ever turn your head unit volume without introducing clipping.  Next, leaving the head unit playing the tone at the just-below-clipping point, slowly increase the gain on your sub amp until you again hear the tone change, then back it off.  Leave the gain set here.  You have just matched the input sensitivity of your amp to the maximum non-clipped signal from your system.  Turn the volume down and remove the test CD (and your ear plugs) and you shuld be good to go.  But get that subsonic-filter if you want to keep that woofer for a while.

Most people don't realize the significant power that a bass boost requires.  I have seen many people do the same thing as you, and have the same consequences.  Their Sub(s) ended up blown.