Hello! I want to upgrade my sound system in my Audi a4 2000.
I have a few questions that i need answers to them.
1. i have a non-bose system, and i know that i have an original audi 4.5" speakers on my front doors ( i dont have speakers in my rear doors)
and i want to know if their is an adapter ring from the original 4.5" with 3 screws to a 4" or 5.25" with 4 screws, and where to buy or how to DIY.
2. is it possible and not difficult to fit 5.25" speaker or its requires modification?
3. do i need to wire from the amp to the speakers on the doors, or the i need to wire up from the amp to the HU, and make the connection their directly to the connector that lids to the speakers? if it is even possible
4. do i have space in the door for a crossover for a component system?
5. if their is a guide on how to wire the amp positive wire from the battery to the amp, to this car it will be great

thank very much to the helpers!!