Where do I start?

[buel]

Hi everybody.
I have a 2003 3 door A3 Hatchback with an OEM head unit.
I would like to improve the overall sound - please can I ask where to start?
Head unit? Amp? Upgrade front component speakers?

Any help is appreciated.
Thank you.

 

[Trevor Locke]

I would say start with the headunit, look at Pioneer Alpine Kenwood Sony etc
Is it a single din unit or double din unit ?? Does it have BOSE fitted ??
My car has a Pioneer AVH-3500DAB unit with Bose and sounds lovely, no need for me to change the speakers tbh