My gf s60d is 4 months old now and has the upgraded stereo. I have been telling her for a while it doesnt sound right and even proved it when using the bullseye type balance control to move the sound around from front to back areas....when the back areas are targeted its very tinny and faint (rear seats and the back hatch speakers). Service verified this a few weeks ago and she is in for service now...sub not working either. She never noticed because she drives and when the bullseye is in the center it sounds ok to her. SO... everyone should check their upgraded stereo system when getting the car to make sure all speakers and sub are working. Dont know what the issue could be..maybe simple...but i know some others have has some upgraded sound system issues.