Get a dealer to pull the original build sheet/option list for the car. That will tell you for sure if it originally had DSP. The -119 amp you found would be a perfect fit for your car. That model was used in the E38, E39, and X5 cars equipped with DSP.

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SOLD
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