Not 100% sure what your friend means as nearly all modern gpus have more than 1 display out, whether it be dvi, hdmi, display port, s-video or good old vga.
Seeing as you plan on outputing it to a fairly big display be a good idea to get a card with decent ram but other than that if its just for video playback dont really need anything fancy. Maybe a 5750? might be overkill.
Sorry cant be more precise with my suggestions, really only know a decent amount about the top tier gaming cards as thats all I usually buy and thus research before I do.