Advice needed

[Tony H]

I need to improve the sounds in my standard(for now) B4 wagon, gonna be puttin sub, amp, speakers etc in,
the sub in the back with the amp, im ok with that, but how many more speaker do i need and do i put them where the standard ones are or mount them seperately and use the original ones too ( which are poo )
any advice gratefully recieved.
Tony.