hkamp

Working in this are is cramped and detailed. Cover the areas with towels or soft things to cushion your butt and protect Mini parts. Climbing in/out of the Mini can be dangerous to the dangling rubber seals - BE CAREFUL. Do Not shut the boot hatch on the seal.
The HK amp has what looks like a single plug. It is connected by a hinged lever release to the amp. Flip it up to release and remove the plug.
It really is two half plugs in a shell. I wish I had taken better pictures but the two halves pop out of the shell rather easy. You really don't have to separate them if your wiring matches what I found coming out of my HK amp. Meaning I think you can trust my wringing out of the sources/destinations. It is easier to work on the wires if separated.
2005 HK Plug Input/Output Grey half 2005 HK Plug Input/Output Black half
Cut only the wires that are needed. The idea is to stop the audio flow out to the speakers and redirect it to line converters then to the amps and back out to the original speaker connections. The HU/HK amp functions as normal (i.e. the EQ presets all work fine). The amp knows no difference that you are taking it's speaker output and adding a little kickbutt to it. We are talking about (16) wires. (Oh yeah and the remote wire must be connected to the remotes from the amps) Leave the wires GROUND-KBUS-REMOTE-(2)INPUTS-12VOLT SUPPLY uncut.
Label everything - on both sides of the cut. It will help you to not re-invent the wheel every time you go to connect them. Do Not cut too close to the plug.
I used a (12) terminal screw terminal strip from Radio Shack. A BMW site suggested it -it worked great. The strip allows you to change things instead of unsoldering or re-crimping. I only needed (12) terminals because I combined the two rear speaker outputs into one. The rear speaker is a dual cone speaker. It receives two outputs from the HK amp. What's the difference in these two? My guess (only a guess) is that the HK amp sends out two frequency spectrums to the same speaker. Anyway I figured to twist the two together and use it as a single amp input. In the end it worked fine.
Keep all positive and negative wires properly placed. This will help with phasing of the speakers.
Keep all Right/Left channels in order.
Strip the wire and screw them into the terminal strip. Keep some kind of order. Remember the labeling.
Using wire of similar type or size run the other side of the terminal strip to the Line Converters or connect the Line Converters up directly. I choose to run a short piece of wire over to the Line Converters residing to the rear of the HK amp in the access area in the boot. If level adjustments are necessary after the panels are replaced. You'll need (3) Line Converters. R/L Door - R/L Tweeter - R/L Rear. I chose PAC-35 Converters only because I had previously good experience with them and they were available on Ebay. PAC-35 covered the output voltage I thought I needed.
The output of the Line Converters are RCA jacks/wires. I bought 12 foot lengths. These need to be run back to the seat belt attachment area and coiled up in the seat bottom awaiting the run up through the center of the rear seat under and through the sliced carpet. You now have an audio signal to hook up to the two amps.
I pre-cut the returning speaker wires. Allow enough length to not only to reach the HK amp area but to lift up and prop up the false boot floor. (6) pairs are needed. (12) wires total.
Attach the returning speaker wires to the already cut HK speaker wires. NOT THE ONES GOING TO THE LINE CONVERTERS. I again used a terminal strip but you can crimp or solder. Make sure of good connections at all costs - you do not want to have to pull these panels off again.
Put the two halves back into the shell and plug (use the lever) back into the HK amp.
The remote wire (usually blue) also needs to be run from the boot area to the HK amp area and spliced into the white HK remote wire. Again leave some slack.