DSP amp replacement with aftermarket - anyone interested?

As well as my lead-wizardry for using aftermarket HUs with H/K systems, I'm now starting to look into a way to replace the DSP amp with an aftermarket one, retaining the stock HU & speakers, for those with broken DSP amps who don't want to shell out £500-odd for a new one (or £300 for an ebay one!)

Just want to gauge interest really before I get too deeply into it - as it is somewhat more complicated than replacing the HU. My research thus far suggests it's possible, and that I should be able to produce a box of tricks for around the £30-40 mark.... possibly cheaper. (Obviously, you'd have to buy your own amp, and you would lose the actual DSP functionality)

Two possible ways forward in terms of fitment - since the connector to the amp is bespoke, and unlikely to be available anywhere - either

1. Cutting into the loom and making bullet connections to the wiring (for which my intention would be to provide full colour-coded intructions and bullet connectors to crimp on), OR -

2. Me butchering your dead DSP amp to get the connector socket out, and providing a complete plug 'n play solution that leaves your loom intact.

The first method has the disadvantage of being permanent (although with the possibility of restoring the original loom at a later date by crimping bullet connectors back to the plug), the second has the disadvantage that you'd have to send me your knackered DSP amp for me to cut open.

For anyone who might be interested.... quick show of hands as to method 1 or 2 being preferrable?

Update:

I've spent all last night and most of tonight doing proper research and looking for suitable components. I now have a list of components and two circuits designed - a transformer-isolated input to link the OEM HU output to an aftermarket amp, that also incorporates the sat nav audio, and 4 passive crossovers for the output side to send the right frequencies to the right speakers.

Having spent the afternoon pulling door cards off and probing the wiring with an oscilloscope, I've discovered that the -3dB crossover point is at approx 500Hz, and that all the speakers are 4 ohm - so far so good.

Turns out that cheapo transformers just wouldn't be up to the job - you need wideband, low insertion loss ones specifically designed for audio, with a small attenuation circuit to drop the levels from the head unit down to line-inputs, and to isolate the balanced outputs from the HU so they can be plugged into the unbalanced inputs of an aftermarket amp without any 'buzz' being generated. They also need two primary windings so that the sat nav audio can also be input whilst remaining electrically isolated. Took some doing, but I finally found one up to the job.

Bad news is... they're not cheap! With 4 crossovers, and two high-quality transformers in the mix, the final cost is going to push nearer to the £60 mark. Having said that, a suitable amp can be had for around £50-60, making the total cost of the switchover still a hell of alot less than even a secondhand DSP amp on ebay.

Drawbacks - you won't be able to adjust the volume of your sat nav input with the current circuit, although it will be set louder than the HU output. I will investigate the possibility of making it adustable with a potentiometer, but since all this rig will live with the amp behind your soundproofing, it would have to be adjusted when fitting.

Also, I still haven't yet found an easy way to plug the whole getup into the loom directly using the existing plug. Anybody got a scrap DSP amp they no longer need? Or even a scrap loom plug?

Would you believe I just dumped my old amp that had been floating about for the past year !. If its any help the bmw e46 uses a amp with the same connector.