I second BSW. I don't have the premium sound and am curious how their new E70 Stage1 will sound. I like thier pnp and impedance matching. I just got thier stage 1 for my e46m3..I'm running my own W7 sub.

I also considered installing the premium sound, as I've done HK swaps into non-hk cars, but not sure if it's as simple with a DSP equipped X5...I'll have to do research. In addition, I haven't heard the premium sound, so I'm not sure it's worth the swap....certainly you can get better sound aftermarket, but I usually like to keep the car oem-like as much as possible.

$0.02
Jeremy

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07E70X5 - 4.8i
03E46M3 - Cpe
98E36M3 - Cpe