So it appears I had the DSP option (and the VIN decoder confirms this). I'm super confused now though. I go to Crutchfield to look at headunit options and this warning pops up:

"When you replace the factory radio, you'll also need to replace the speakers, run new wire from the radio to the factory amp location, and splice into the factory speaker wiring to bypass the amp."

I've had the door cards off and the speakers are definitely original, so somehow this aftermarket Sony unit did not require new speakers. How could that be?

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2003 X5 3.0i MT, White, 161k