Hi everyone! I have a problem. I am sharing my car with my brother, a Kenari Aerosport (2006), and everything is stock for interior except the Head Unit which I have changed to a Sony which i dont know model, but basic one around 200 which accepts AUX.

As you can see by that statement i am quite the idiot in terms of audio stuff!

Now my brother is suggesting to get a subwoofer, tweeter or something else idk, because apparently he doesnt feel that extra "oomph" from the bass. I agree, the bass is pretty ok but while driving 100+ cant feel it if windows down. And if volume above 25+, sound gets distorted like speaker pecah. But below is fine.

Its all stock speakers in the car, 2 front at side door, 2 back at roof
With all that said, he is willing to pay for everything but dont know where to go and takut kena tipu–same for me. He has a budget of 300. I can probably top it up to 400-500, but preferably 300-400 spent. Dont want to spend that much on a old car which he is using more nowadays.

I would gladly appreciate advice on this matter and about the budget, and where i should go to get this done!

Thank you.