Monitor size?

I want to put a monitor in the facory drop down bin but i dont know what size will fit. I wan t to get the biggest one possible but i need to know what size you guys have used. Ive been looking on ebay but i really have no idea which one to get. Will a headrest monitor work and if so do the have one that swivels so the kids can see it better in the factory bin? I also want to know if i just hook the monitor and player to power and use an ir sensor with headphones do i have to go throought the factory av system? this is only for my 2 kids in the rear so i really dont want to hear spongebob while i'm on the road. One last thing i have a chance to buy a myron and davis monitor (7"new) for around 275.00 but it is brown and i have grey int. is it possible to paint it or should i just go with a cheaper ebay model. Sorry for all the ?'s, i just want to do thids once and do it right. I already have a Blaupunkt MER player and i actually have a stand alone flip down monitor(both uninstalled) but i want more of a factory look with the ability to use wireless headphones Thanks, Alex