Improving Audio Quality in a 2018 Baleno Without Replacing Stock Speakers

Improving Audio Quality in a 2018 Baleno Without Replacing Stock Speakers
Hey everyone,
I have a 2018 Maruti Suzuki Baleno with the stock speakers and head unit. I’m looking to improve the overall audio quality without replacing the stock speakers.
I’m not a bass head, but I do feel the bass is a little lacking. More than loudness, I’m looking for a refined, balanced sound with cleaner vocals, better instrument separation and slightly fuller/tighter bass.
My budget is around ₹5,000.
I was initially thinking about adding:
Tweeters
A small powered/under-seat subwoofer
But I’m wondering if that’s the right approach at this budget, or whether I’d be better off with front-door damping + speaker sealing first.
For those who have upgraded the audio system in a Baleno while retaining the stock speakers/head unit, what would you recommend?
Would love suggestions for specific products/installers as well.