I've had mine since early May, just lost the first door speaker. I won't lie, I like to play my music somewhat loud (iPod), but it's mainly a function of driving with the windows down whenever weather permits, and so I put it up a little louder so I can hear it more. I usually play it around 18-22 with windows up, and around 25-29 with windows down.
When I think about it, I have had some passengers that have decided to take over and put it up in the 30's; but I don't think they've taken it up to the max.
I'm gonna take it in this afternoon, we'll see what happens.