304 pounds of audio in the trunk -might- be the cause of your ass sinking into the pavement
bad struts would cause your car to bounce when you push down on the area that you think has the "blown" strut.. the more worn out the strut is.. the more it bounces.
a "good" strut- you can press down on the car and release and the car should come back up and stay in the upward position and not move