[f5fstop]

How it sounds is personal, I like it, and it for me it has plenty of bass and clarity of high signals.
As for speaker replacement, all speakers are replaceable with aftermarket speakers, except for the rear, which is not subjected to weather problems.
The rear speaker is replaced as a box, but it is not required to purchase the amplifier, it is serviced separately.

As for satellite radio, can you get Worldspace satellite in Germany? If so, you might be able to switch out the XM receiver box for a worldspace receiver. They operated quite similarly, especially since Worldspace is one of the owners of XM, and they have co-developed many of the units used by each system.