Aftermarket audio options?

[thatoneguy...]

Hey all!

Hope this is the right place. I have an '09 135i (I believe it is an earlier one, as I have tweeters in the doors and the sound system isn't too bad as is), and I'm looking at upgrading the sound system. I'd like to keep the head unit for that clean OEM look while running an aftermarket amp to give the speakers (which will also probably be aftermarket, unless there's a very good reason to keep them stock) more punch. I just haven't seen an outline of what years had what speaker layout and what sizes fit. I know that early '09's had a subwoofer under each seat, but sizing/location whatnot has me confused. Any help would be great! Thanks!

Edit: Found this thread which has a speaker layout from 2009, is this accurate?

[Gangplank]

There is a ton of info on the forums here on this. That said, for ease of choice, upgrade in stages & install I'll probably be going with BavSound

Stage 1 - speakers
BimmerTech amp - plug & play harness
Underseat subs

https://www.bavsound.com