2010 135i Audio Upgrade Advice

Hey guys just picked up my first 1 series. It’s a 2010 135i manual m sport and loving it so far just not too enthused with the audio.

As far as I know it has the base audio system (no pillar tweeters) and in 2010 was worse than the rest of the years which came standard with Hifi. The car does not have I drive or anything like that which I’m ok with but I am getting a 9” head-unit so that should help the sound a bit (4x45w output built into that).

My question is what upgrade path is recommended to get better audio in the car?

Is there a way to splice in a set of the pillar tweeters into the standard door speakers as I found a set of those for reasonable. Or what speakers and amp and all that are recommended to wire into the car?

Also is there a replacement for the under seat subs that would work ok?

Not super knowledgeable about radio upgrades but know a little and have some friends that have installed big systems before so not afraid to tackle it myself. Just don’t know where to start and really where to post this so hope this suffices

I appreciate it!

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