better to change the head unit or 5in from the front?

[Stembo69]

Have a Tevion head unit that was in when i bought it, unsure what from speakers but suspect they may be alright as there are Infinity tweeters fitted.
TO get around the sound distorting and get a more solid bass would i benefit by changing the head unit or speakers as a 1st port of call?

[Predator_R32]

mdf speaker rings for the mid speaker and sound deaden as much of the doors as possible and you will get decent sound from them

also fiddle about with the settings on the headunit/amp