TG, sorry to hear about your ballast/xenon issue. Mine came xenon standard, so I don’t have much personal experience with aftermarket xenon, but could it be that the ballast just need to be secured better? Just guessing.
WRT stock speakers. I totally agree with you, I haven’t heard and stock stereo that’s as good as aftermarket ones. All the stock systems I know runs on 2 Ohms, not 4 Ohms like most aftermarket ones. So, although the sound at average decibel is decent, when you start to crank it up, you’ll see its limitation. Not to mention subwoofers. 8″ can’t produce the kind of low notes that a 10″ or a 12″ can do. Size does matter with subwoofers. They also need space, so under the seat is not really ideal for subwoofers. All stock systems I’ve heard so far do lack power. It’s not a BMW thing. It’s cheaper for them to put the weakest amp they can that can be sufficient for your average buyers. But for audiophiles, they’re totally unacceptable.