You are more likely to make it worse than better by fiddling around with aftermarket speakers. Several folks will tell you they have made it “sound much better” by replacing speakers in stock locations but the reality it is will just sound different, not necessarily better.
If you really must change something, things like improving power supply by whatever means will help in those situations where the amp is under heavy load, so this could be a +1 for battery/power improvements.
For speaker swaps, you need to be matching amplifier ohms loads and things like the FS of speakers (or at least know what you are doing with those things), as random speaker X will not always do what you expect.
If you class yourself as a true expert on audio in cars, you would potentially get to a position where you do the swap and end up admitting to yourself that it’s worse than stock. Very hard for people to do, you need to find a way of measuring an improvement and knowing why it got better. Or indeed worse.
Always a very opinionated and emotional subject, the hardest bit to learn about sound in cars is usually most folks don’t know what they are doing and usually you can be told something is better and believe it because your brain tells your ears to believe it.
First try and be really clear with yourself on what it is you are trying to improve.
The speaker positions dictate a lot about how the sound will behave - side window reflections, windscreen reflections, bass frequency gaps due to sub location, lower vocal capabilities due to separation of midbass/midrange etc. If you really want to deliver a proper improvement you have to match products to these constraints, not just pick random bits of kit.
Honestly, I would leave it alone - but maybe If you have to play with it - on a car like the model 3 I would go for battery strengthening, improved deadening/dampening and finding a way to integrate a full DSP/processor into the OEM electronics. Then it can only be your own fault on setup of the sound, not related to any particular product that someone told you sounds better.
Once I get my model 3 I’ll do as unbiased a review as possible on the sound characteristics and where the strengths/weaknesses lie, I don’t mind sharing this output, kind of missing not having time to compete in and judge sound quality competitions any more. However this will just be an opinion and not a definitive guide as we all hear differently and we all have different opinions/emotions about what sounds good or bad.
I have not been much help to you there ... lol.