Improve the sound... or improve your rep... two different things.
The oem, or aftermarket rear speakers do a fair job of improving the sound, I recommend them (I have the oem rears, and they were a definite improvement).
But, it's a roadster... the accoustic engineer's nightmare! It is by definition
limited.
You can add multi-$$$ sound gear and be able to impress your friends.
But a convertible can not possibly have truly good sound... it's not isolated from the sounds of the street, especially with the top down - no way, no how, especially when compared to an enclosed coupe or sedan.
There is no right or wrong.
If trick gear is your thing, go for it.
But temper your expectations, there's only so much you can achieve.
