I picked up a new vehicle that has 4" speakers in the front doors, and tweeters up on the dash.
That said, I'm having a hard time finding decent 4" components that won't put me in the poor house. Ideally I'd like to spend around $100. I've used JBL components in the past with great success but cannot find them in 4".
They'll be powered off the head unit. Just need a decent component set with nice clarity that gets loud. In the rear I have two 8" subwoofers that play 50-120 hz, and a 12" sub that plays below 50hz.