Just got avic f 90bt,diamond HEX s600s speakers and JL amp A4300 for my ford F-150 06 extended cab.Is this good combination?

Sounds like a good combo. My thought is that more power is always better. Under powering speakers, in most cases, is what causes damage. Your JLA4300 is a good amp, the DIAMOND HEX S600S will be better than putting 5x8's or 6x8's in (circular speaker have less distortion due to shape than oval speakers), and the head unit is a good choice for the price.

Let us know how the install goes.