Help Me With my System

Using a factory cd player out of a 98 Z28, I have a 10" kicker comp VR in a hatch box with a 400 w amp that only half the amp is powerein the sub the other half is open to 2 more 6.5 in speakers i have the factory delco speakers in right now and dont know what to buy for my 4 other speaker replacements. Any brand specification and if i should hook the front speakers to amp of the back pair. i was thinking maybe kicker speakers all around or boston acustics all around but there pretty pricy.

Thanks for any replies

Max