[brimmers]

Hi all, I bought my 56 E92 two weeks ago and I love it, apart from the audio system.

I've done a bit of reading and discovered I have the Base audio system, with no nav or bt upgrades. My plan is to install aftermarket speakers and an amp to power them to give a bit of a boost to the current system. This is my plan:

Install Focal Audio 165AS3's in place of door 4", underseat woofers & adding tweeters to the door (requiring new trim).
Install a bridged 4 channel amp to drive the crossovers & speakers of the above speakers (probably an alpine, TBD).
Recode HiFi to Alpine setup in order to flatten EQ, whilst retaining rear speaker channels from OEM HU and to keep PDC.

My questions are:

Has anybody had any success fitting 3" drivers in place of the 4" ones? I figure with smaller drivers I'll be able to fit them a little bit more flush to the OEM grilles, allowing me a few more mm behind to contain the drivers. (Failing this I'll just sell the focal 3" on and replace them with some 4" mid-ranges that are proven to fit in the E92 doors).

To drive the amp I plan to use speaker level inputs, driven from the FL,FR speakers outputs from the OEM HU. To run the 4 channel amp bridged, I will need to run both FL,FR & RL,RR speaker level inputs into the amp. Can I just fork the FL,FR inputs so that the OEM FL,FR are connected to both FL,FR and RL,RR on the speaker level inputs of the amp, or will this cause any damage? (The speaker level input impedance is 10kOhm if that makes a difference).

Coding is another issue all together, I think I may be leaning to just paying the dealer to do it for me... Or is it worth the investment in the coding kit and skills?

Thanks in advance for any help!