4 channels amplifier

Hey there,
i want to amplify all of the speakers in my chevy cavalier 98. My headunit is a Sony xplod CDX-GT 220. Did i will get a better sound / bass with a cheap amplifier (Like the Pioneer Sony GM-4300F) ? And i got alerdy a subwoofer and my headunit got only 1 RCA Output.. actualy i use the subOut to control the subwoofer.. The best will be to change the headunit ?

you wont have to change the head unit. (personally i would cause i'm not a fan of sony, but if it works, don't fix it lol)  one thing that would be nice to know is what speakers do you have in your car now? are they factory or aftermarket?  if there factory, change them, then listen and if you want louder then amp.  but if you'ev already changed the speakers then you would need to look for an amp with speaker level inputs or use a line out converter.  as for the amp providing better sound or bass...that will mostly depend on what you have for speakers. but  you won't have to change your head unit.

-------------
Tri County KustomZ
certified installer

Indeed it will be best to change your head unit and get a solid one with 3 preouts, preferable high voltage, low impedence. Then save up some more $ and invest in a amplifier to drive the front and rear speakers. Of course you can do both and watch your system come alive at the same time.

-------------
Top Secret, I can tell you but then my wife will kill me.

I got aftermarket speakers and they sound great but not enough bass. Thx for help the line input on the amplifier is a good option!