I take your point but with Hi-Fi (different I know) if the signal is top quality then you will get the best out of all the components down the line. So if the limitation is say the signal from the amplifier (or the head unit), then it doesn't matter how good the speakers are, the sound will still be compromised. If however the amplfier is producing a high quality undistorted output the original speakers will work at their best.

I have seen a high quality 100w amp feeding a stock speaker from a citroen saxo (rated at 10w) flat out with no problem, but put the slightest bit of distortion in and the voice coil just gives up.

The original speakers are at least specially designed (chosen??) to work in the enclosures and environment of the car. The enclosure and location has as much to do with the sound you hear as the speakers themselves and apart from very few examples you rarely see the enclosures being adapted.

Years ago I always used to swap out the original speakers in cars to improve the sound and apart from an initially sharper top end (which is usually tireing to listen to for extended periods) there was little gain in real musical quality.

I understand that part of the problem with the Euro versions of the X5 is the active crossovers built into the amplifier. If you by pass the OEM amplifier you have to build in some sort of crossover to get the best out of the speakers. It may be that the system installed in the US is different so different solutions may apply. But it is interesting to note that Pete M found that there was little benefit from the speaker upgrade until he upgraded the amp. It would be interesting for him to put the stock speakers back in now to see how much difference there is. How about it Pete? Just for research so to speak!!!

Oscar