Aftermarket amps w/DSP HELP(JimL or Bob Hazelwood) (archive)

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My 1999 540i is in the stereo shop getting a sound system overhaul. They've built an awesome fiberglass subwoofer enclosure that replaces the batter compartment cover and it looks GREAT. I am using a single JL Audio 10W6 powered by a PPI PC1800 amp. I am also replacing the front and rear speakers with Diamond Audio, two-way separates up front and two-way coaxials in the rear package shelf all powered by a PPI PC4800 amp.

However the problem that they encountered is hooking up two PPI amplifiers to the "premium" DSP/amp.

I have read numerous postings in this board pertaining to this DSP/amp, but I have not found a difinitive solution. The shop tells me that I MUST keep the DSP/amp and use the speaker level outputs from that as the inputs for the new amps. Is this true? They also said that all of the radio controls (tuner etc.) are contained in the DSP/amp and the head unit is really just acting as a remote control. Is this true?
Is there anyway to bypass the DSP/amp all together and get a clean signal to feed the PPI amps?

By using the existing DSP/amp, each set of speaker level outs are already crossed over to the BMW crossover specs and therefore a full frequency signal can not be obtained to feed the amp for the mids and highs. They suggested that I add a third amp into the system, so there would be 1 amp for the sub, 1 amp for the mids (front and rear) and 1 amp for the highs (front and rear). However the problem that I see with this is since the premium system in the 99 540 has 3 speakers per side up front, the DSP/amp is crossing over highs, mids and mid bass for the front, but my replacement speakers are only two way, so do I use the mid or the mid-bass from the DSP/amp as the feed for the midrange? Either way I do it there will be a hole in the soundfield.

The other thing I have read about here and have considered, is if the DSP/amp is indeed Alpine and controlled by the AiNET, could the stock DSP/amp be replaced with an Alpine product such as the PRA-H400 frequency processor? Does anyone know if there is a product that is compatible the signal from the head unit and would work with the head units controls for tonal adjustments as well as the DSP settings?

As you can see, this is a very frustrating process. If anyone has figured out how to correctly install aftermarket amps with the DSP system, I would love to get your feedback.

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