Here's what we ended up with:
We went back to the model at RadioShack. It's a Go Vision TV/DVD Travel Theater. It also is a CD and MP3 player. It is $499. It has a 10.4" screen and comes in a case that can set on the floor or on a headrest. It comes with straps that attach to the seat frame. It has a back flap that folds out to a wedge to support it at a slight angle. It also has a "visor" above the screen to prevent sun glare. It has a TV tuner and can be adapted to a lighter, A/C-D/C plug, plus it can adapted to another TV to use the CD player only (like at hotels without DVD player). I'm watching it right now (Lord of the Rings) and it's not bad. We bought 3 headsets for each of the kids so the highway noise won't interfere with the sound (or the sound won't interfere with my nerves...)
We were assured that if the price came down w/in the next 30 days, we can get the price adjusted.
I might add, I was reading the owner's manual, and learned you can also connect a camcorder, game console or digital camera. Considering all the extra features this has, we thought the price was worth what we would get out of it. One of the things my son has been begging us for is a t.v. in his room. I think he's too young to have full t.v. access. But when he has his buddies sleep over, we can set this system up for him to watch dvd's in his room and not disrupt the rest of the family.