Few would argue. The weak links are the amp and speakers. The head unit is OK.

You can do the DSP upgrade, but that is a ton of work and the coding is a challenge.

The other option is an amp and speaker upgrade plus add a subwoofer.

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2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input