Basically the current setup I have is pretty rubbish. I'm not complaining as it IS just the OEM basic audio system and in many ways that's the best starting point.

I have been going over and over things in my head as to quite what I want to do. I have a VERY good set of Nakamichi kit, but the amps are a bit too big to go where I want. OTOH do I really want to buy a load of new kit and keep storing the Nakamichi stuff. Decisions decisions.

The X5 needs (deserves) some good amps and good speakers. With the 6 possible speaker locations up front, that would lend itself to a bi-amplified set of 4 plus a pair playing a centre channel (derived from L&R with an Audio Control ESP3, which I just happen to have). The rear doors could just have the mids, but I may end up putting tweeters in there just 'cos I have them. But I want them to be masked from the front occupants to avoid confusing the stereo image.

2 subs will be mounted in the rear luggage space - how, yet to be decided, but I have some ideas.

Amp location is an issue, also yet to be finalised.

Don't seem to have got very far do I:-)

In a way I quite like the idea of using an OEM DSP amp and feed all the outputs into some decent amps. That way you get control via the head unit display/Nav screen and good sound. But the active crossovers programmed into those DSP amps leave much to be desired (specifically a big chunk of the sub range). I have heard it said that this can be corrected with re-programming, but I've yet to have that confirmed. I am at a complete loss as to how or why BMW put so much effort into designing their flagship audio system and yet bizarrely leave a big hole in the sub output - not to mention its other shortcomings.

Ideally I want a Dolby ProLogic II decoder. How come BMW stick in a DSP amp, yet don't include a decent decoder that can actually make use of Surround encoded music. Unfortunately, I don't yet know of any decoder that could successfully be used though:-(

One thing I still need to ascertain is the actual size of the OEM mids in the doors. I have seen this specified as both 5.25 and also 6.5". The trouble is that there seems to be some variation in how speakers are measured. Cone size? Frame size? Or even the diameter of the plastic grill that fits on the outside. Anyone know the precise dimensions of these speakers?