Speaker sound is uneven
 

Hi all,

I 've got a pair of 100watt 6.5" speakers in the front and a
pair of 500watt (supposably) 6x9" speakers in the my parcel shelf, all
4 speakers run off 1 450watt amp. For sometime now the sound has been
louder towards the rear of the car so today I changed the 6x9's for
another pair of 160watt kenwood 6x9's. The sound has become even more
directed to the rear of the car.

Can some please tell me what I can do to even out the sound so that it
sounds better.

thanks