Car speakers?

I know this is a little out of the realm, but a friend is looking for 6x9 rear speakers and 6.5" component speakers (with separate tweeter) for the fronts. He's looking to spend about $150 for the rears and $300 for the fronts. I think he'd stretch a little if there were significant improvements to be had. Haven't looked at this stuff in 20 years so any thoughts/recommendations would be greatly appreciated. He may also need an amp so any thoughts there would be helpful as well.