I finally did it. I didn't order my R60 with the HK system because I didn't think the extra $750 was worth what you were getting. So I wanted to put together a system for less then that, but sounded great. I wanted a system that had better quality not blast your ears off loud (been there done that). I figured an upgrade to the front stage was all that was needed.

What I am running:
Pioneer 4 channel amp
Alpine (budget 3 way) 4" co-axial, 6.5" component, all ran by passive 3 way crossover
Pioneer Shallow Mount 8" sub
Clarion Equalizer
Audio Control LOC

It cost me under $500 for the whole build and it was well worth it.

There were some setbacks, and the system is not perfect, but it is a huge improvement. I could have spent more on the system to get it even better, but for the volume I listen too this great. It leaves more money for other mods!

Install tips for er'body:
The X9331 is not the same for the countryman, The wires you want are going to be same color as the ones for the under seat speakers, but make sure you do a bit of phase testing with your under seat speakers so you know what is truly positive and negative.

The Equalizer is a must. Maybe because I am running an odd 3 way setup up front, the Mid were really loud, having the crossover to dial them down and bit and blend the sub with the 6.5" speakers.

The Audio Control LOC is awesome, it has a signal sense turn on circuit, helps eliminate the need to find the infamous radio on cable.

Below are the pictures of the install. Don't mind the dog hair, My dog sits in the cargo area, and he gets Hair EVERYWHERE; the MINI needs a bath badly. Anyway picture one is the signal processing etc, the sub is next to it and it all fits nicely under the flat load floor. 3rd pictures is the 3 way crossover for the front speakers that is under the front seats. I already tor out the stock speakers so i cut a bit more carpet out to mount the crossovers on some MDF. Used box carpet to cover the wood and left about an extra inch to cover up the gap / where I cut the old carpet out. 4th pic is the placement of the tweeter, I got the idea from another thread on here, great thread for advice by the way. The last picture shows the under seat 6.5 with the speaker cloth covering it.

If you have any questions let me know and I will try to answer them as best as I can. Hopefully this might encourage more of you to not settle for what MINI calls a sound system.

 

Question: how was the Audio Control LOC in the boot fed exactly? Did you only use the wires feeding the under seat speakers? If so, I can assume they were full range then? I have been trying to figure out how to get into the X9331 to also tap into the door speaker feeds. Was curious if you tried that as well. Or did you do home runs to the door speakers? If so how did you fish wires through the door umbilical?

 

I tied into the stock stereo at the X9331ish adaptor. If you tied into just the under seat speakers, you would only get mid-bass and lower. The Adaptor has a few other wires and all the speaker wires going through it, the right front is yellow based with some stripes (can't exactly remember the color) and the left has some red violet stripes on black, I think. They are the same colors as you see when you pull out the under seat speakers.

The little adaptor is in same place as on the R56s, in the drivers side foot well. Just pop off the kick panel (easier said then done) and you will see a translucent white adaptor. In the R56s there is the magical radio on wire, the R60s don't have that in it or I have not been able to identify it. That is where a LOC with signal sense comes in handy.

I ran the 2 coaxial 16 gauge wires down the side below the kick panels on the driver side. You have to take out all the seats, and kick panels to make this happen, and take out part of the rear boot floor moldings to get the wiring to snake into the lower boot floor area. Along with the signal wire from the X9331 like adaptor, I ran another 2 coaxial 14 gauge wires to allow the amped signal to feed the crossovers / front speakers. The bundle was 4 coaxial wires, not really small, but I got it all to fit just fine.

For the under seat 6.5 and new tweeters I ran new wiring from my crossover, for the mid range 4" I used the existing wiring in the car. I tapped into that on the other side of my X9331 adaptor. I cut the wiring on the top part of the adaptor. I disconnected it, and pulled it out a to get to the wires a bit easier. Cut the fronts, and tested which end got signal by quickly connecting a signal to the cut wires. If i heard the sound, I know that end was going to the speaker, and the other end was from the head unit, then wired appropriately.

I never really fussed with the umbilicals to the doors, too much work when I can just use the wiring already there. I know it's small (20 gauge?) but for me the amp is only pushing 40watts RMS and the 4" speakers are only handling 500hz to 2000hz, so the cable shouldn't be over run with current.

I hope this helps a bit and I wasn't too long winded.

I noticed you are in PDX. I am in Woodstock area, and work downtown, feel free to hit me up to see / hear it in person or just chat about the MAXI MINI. I use to be in PDX MINI group but had a kid a year ago, and well they suck up a lot time. Maybe I will return to the group soon.