1. why do you say epias are basic? I have an epia and I do everything you listed and more. I mean what did you want to do in your car that would make the EPia basic? that's your first answer
2. also answered by #1
3. there is a pansonic slot load dvd floating around on ebay look for that. Otherwise you can run a usb/firewiree (ieee-1394) drive up front to eliminate the long ide cable problem.
4. as for placement the best and easiest location would be in the trunk, I dont understand how this would interfere with your backseat passangers. Also if you go with the trunk route get any motherboard that you want, slap a beefy video card, maybe a mobile processor for less juice, etc... feel me?