Hello, the R129 MOPF with original BOSE sound system has an amplifier in the storage compartment behind the driver’s seat. This BOSE amplifier has 5 channels (VL, VR, HL, HR and Sub). In the R129 this BOSE amplifier uses 2 channels (VL and VR) on other Mercedes models on the input side of the BOSE amplifier uses 4 channels (VL, VR, HR and HL). I love to use speakers from Visaton with an impedance of 4 ohms. But if I’m looking for an amplifier with 5 channels (VL, VR, HL, HR and Sub), then all have 5 channels on the input side. Which amplifier can I use to control 5 channels output with 4 Ohm impedance from 4 channels? Thanks and greeting P.S. A few more photos to my other thread (R129 retrofit BOSE harness) will follow…