Decisions, decisions!!

[el_duderino]

It's actually around $350 if you get it from Crevier BMW.

The SQ of the HU to an aftermarket amp is the same whether you have DSP or not. The articles state that once the DSP is properly bypassed, the OEM HU to aftermarket amp interface is the same as it would be on non-DSP vehicles.

The interface after the amp is not needed at all. The non-DSP systems have front and rear full-range balanced analog outputs. I personally run them through Iso-Max isolators (flat to 0.5 Hz) but you don't have to, I guess.

You had better be planning on buying a very expensive head unit if you want it to outperform that OEM HU, once properly interfaced with. If executed properly, your limiting factors are your amps and speakers, not the HU.

Tell you what. I'll happily tell your installer how to do it.