We have a 2011 X55 and love it.
36 qt but probably not worth $$. I bought a soft cooler off MCbyDesigns. Probably the best $50 I've ever spent on a cooler. We use the factory one but it's in the way when surfing due to placing our sacs, plus it don't keep ice very well.
I've had trouble with my iPod but think it was the cable. The USB in the head is the only one for media. DD's iPhone would cut off when she Got a call or text. You have to set the iPhone on a certain setting...can't remember right off what it's called.
Sorry I can't help, we didn't have presets stations since we can't pick up stations on our lake very well.
It's been answered but yes, mid-ship plug under round plastic cover under carpet.
One tip. If you have kids make sure to tell them the ladder MUST slide all the way out before flipping it over into the water. My kids or a guest didn't. Extended the ladder and flipped it out which chipped the gel coat above the rub rail. 55s need a bar there so it won't fold out unless it's slid completely out. Or, just tell the kids not to touch it!