Anyone explain the differences between head units?

[OrangeCrush]

Any gurus able to explain the differences between Pioneer's AVIC-N1, N2, D1, etc, etc???

I've looked at Pioneer, Alpine and Eclipse. To be totally honest, I have no idea which one suits my needs.

Several things.

I want nav, that's a must. DVD I am assuming can be used in place of Nav but only one or the other.

Obviously I want it to play CD's. It must be able to host a rear view camera.

Also, I prefer the Nav or dvd to be included in the same unit. I don't want a separate unit.

I want touch screen.

Can anyone make a suggestion. I'm worn out looking at them.

Thanks,

Mark

EDIT: Oh yeah, one more thing. I want the screen to be part of the dash. I don't mind if it tilts out to insert CD's but I don't want what I had in my Yukon... a motorized unit that can fold away. Hope that makes sense.