Happy to help mate,
Wow, you certainly know your stuff!
It's not going to be a cheap job, but I'll be looking into it and costing it up.
With regards to dropping the back seats I do need to fold them down a few times a year so the MDF sheet might not work but I was thinking maybe cable ties/tidy as an alternative.
Getting to an aftermarket stage isn't cheap but is necessary to be able to fit the good stuff,
You could build an MDF panel to span across the double seat meaning its still foldable in stock 60/40 style, while incorporating a 20mm cavity for cables.
There's also fish net cable sleeve looks good,
See link: http://www.ebay.co.u...=item43b5e50b25
Some money can be saved in labour costs by routing some cables yourself,
You can also improve audio response by fitting these when fitting your speakers:
I've got some brand new carpet and cable may be of interest if you do decide to go ahead with it,
Just saying no pressure or obligations i wasn't leeding up to it or anything it may help you though: http://www.fordowner...ade-items-sale/
I've planned my audio upgrade last September, I've been purchasing parts since then with the view of completion in may as you can see on my build thread.