My friend has a '97 civic hatchback...perfect for a system. I already have a sealed box for him and getting 2 polk gnx104's in it. He currently only has 2 6 1/2 speakers in the doors and there's a place for 5 1/4's or 4x6's in the back. I was going to ask if it would sound good to just get really good speakers in the doors, and then get a 4 ch. amp to drive the speakers and the subs. Thanks!
From personal experience, I used to have a 91 Integra, which is a hatchback, with 2 10's. And it did make a little difference in loudness with rear speakers than without. But I wouldn't get great speakers for the rear, just something upgraded from factory. Hope I could help.