Nakamichi fitting

[UKenGB]

I have 2 pairs of Nakamichi SP50/SP10 component speakers with a pair of their PA300 amps and a pair of the SP-80 woofers with a PA400 amp to drive them. These are quite old now, but they were quite stunning when I last had them in a car, however I haven't needed to use them for a while and I'm thinking I could use them to liven up my X5's audio. I was hoping for some help regarding several aspects of this.

My X5 is the UK model with Nav and standard audio (and CD changer, but that will be coming out). Is there any form of external amp - I cannot easily see where that is as there doesn't seem to be anything by the CD changer/Nav DVD rack? Is it integrated with the radio module? Isn't that in the cassette unit?

I will need to get access to the line signal output in order to 'insert' the amps but I've no idea how to achieve this. Are ALL signals routed via the back even if there's no amp there?

AFAICT there is NO tweeter in the front doors, just the mid bass in the doors and something in the dash by the screen which sounds more mid range than tweeter. The rear doors have a pair of mid bass ONLY - also NO tweeters. So it would appear to be a 6 speaker setup.

How do the speaker signals get to the speakers? Where are the crossovers? Where do the wires run?

What size tweeters can be fitted in the front doors (behind the mirrors). My SP-10s are about 2" diameter, could they be squeezed in there?

Perhaps the biggest problem is where to fit the amps. If I put a sub in the RHS rear space there's no room there. Are there any hidden spaces that could be used behind the panels around the rear boot/trunk space? Any room under the rear seats, doesn't seem likely to me? Has anyone put amps under the front seats? The 3 Nakamichi amps are all the same size, about 13"x7"x2.5", but I may need a 4th in there. What about a raised rear floor, anyone done this?

Just looking for ideas at the moment to help me figure out how best to do this.