2017 facelift Octavia VRS audio upgrade

Hi everyone. I've had my facelift Octavia for about 8 months now and put on about 10k miles.

Absolutely love the car but there's one thing that bugs me about the car that Im hoping to address: The audio.

Its poor quality, crackles (on certain frequency ranges) and has no bass at all.

I believe my car came with the MIB2.5 and the basic audio package and Im looking to upgrade the speakers and add a small sub into the car.

Im not looking for window shattering bass. just something I can actually feel

My only requirement is to keep the current MIB headunit in the car.

any suggestions or tips or anything at all would be so helpful.

This is the first time Im doing an audio upgrade on a car that wasn't from the 80s or 90s so Im guessing alots changed