You can't compare those brands in those premium cars. 9/10 of those cars are specifically tuned with the car shape, size, interior, windscreen, dash material, etc all in mind. But if you compare a highly tuned Bose and compare with my setup that's tuned as well in my car (meaning both brands in my car), Bose is meh only.
I'm a Dynoaudio user but if you compare my setup vs a stock Volvo that comes with the tuned Dynoaudio setup, I'm pretty sure the Volvo will sound better, but my sub will be better since Volvos will probably use underseat woofers.
Anyway - you can tell I'm ICE gila.
Erm.. I have a friend whose 316Ti has a S3 engine in it (3.0L) without being registered. 1.6L roadtax but 3.0L performance in a tiny hatchback BMW Ti platform. Freaking awesome car.