Remember it's not JUST xenon's.. that's trivial as you can add HID's to any car for about $55 for a quality kit. Putting them into your stock housings (e.g., the base X1's) is unethical though and you'll piss everyone off.
It's the housings which include projectors and adaptive headlights that really make it worth it. Hell the fact that they aim themselves is worth it! Aiming headlights is an unbelievable PITA. Also there is no amount of retrofitting you can do here; aftermarket projectors are unavailable, and even if they were, would not self level or turn.
The base stereo is sufficient and I would not upgrade it.
///M Power - 2011.75 LMB M3 6MT (fuelly)