Idk why mobile video is even a priority for the front seat of the car, unless you spend a lot of time sitting in parking lots.. I say keep it simple.
I did a ton of research and ended up with the Kenwood eXcelon KDC-X595 for a source unit. It has 4V preouts and direct ipod connectivity, along with a 3-line color-adjustable display. $160 from a local audio shop, which is massive bang for the buck in my opinion. Everything you need for good sound, nothing you don't. And don't let anyone tell you 2V pre-outs are fine. The stronger signal is where it's at. Period.
I know it's been suggested, but i'll suggest it as well. Forget rear speakers. They just suck power and muddy up the sound. If the people in the back seat like to complain, they can buy their own stereo system. My suggestion is find a set of front components with a tone you agree with that have a very high sensitivity rating (92db @ 1w or better). That way, you can run them off the head unit and simplify your installation with just a sub amp. 20w will be more than enough for speakers with that kind of efficiency. You may have to jockey with installation a bit, but 6.5" is the way to go. I found a set of components for $150 I am seriously considering. They are made by Hertz, which is owned by Audison (good stuff). It's their entry level speaker, just google them. 93db efficiency, really good tone, and in-line crossovers for a simple install.
For the lows, decide how much you want. Two 10" in a sealed enclosure with 600-1000w will have enough cone area and oomph to give you loud, crisp bass and still leave you with most of your trunk space because you only needed ~1.5 cu.ft. of box. Again, efficiency helps here. Also, a sealed enclosure will be more forgiving for the novice system. Get the cubic feet right and you can make a mistake or two with distortion and not ruin your voice coils.
Any idea what your overall bass budget might be? I say buy the best quality amp you can get, even if it has more power than your subs can take. Speakers do what you tell them to. If the amp is straining to supply the juice, your speakers will let you know in a hurry. Better to underdrive the amp than the speakers. I could make some suggestions if I knew what you were looking to spend on the setup.. $500 for two subs, a box and amp will get you started. $750 opens up a lot of options for good sounding bass. Obviously the sky is the limit. Enclosure size is key. Most ppl screw this up. Read the owner's manual for the woofer, or call the manufacturer if you have to.
You'll spend $100 on a wiring kit (go big, like 2awg) and a head unit mounting kit. No need for fancy rca's, just run power and rca's on opposite sides of the car to avoid adding unwanted noise.
Hope that helps clarify what a good sounding entry level system should look like.
