Yo has any1 just replaced speakers with new sub

[SSVBUDDY]

Yo - it seems changing the head unit is very expensive,so im thinking of keeping the Blowfunket even thou i hate it, but less drama, & changing the speakers- i like having the sound in the rear parcel shelf either 3 or 4 way 6/9 with a sub. Has anyone put 6/9s in the rear?. I would like your expert opinions