Medium.
I use the terms "small", "medium", etc. to reflect a room's suitability for large, high end speakers. Many large, full-range systems produce enough bass to overwhelm a typical 12 x 17 x 7.5 space. Many large planars will physically dominate such a space. In my book, a large listening room can accomodate all but the lunatic fringe loudspeakers.....which need very large ("huge"?, "palatial"?) rooms. IMO, the space the OP describes will probably be too small for best results with a LOT of high end speakers that will work well in large rooms.
That said, when I look at the "systems" links for some 'goners, I see some very large speakers stuffed pretty tightly into smallish spaces, so - evidently - some other might use similar critera and reach a different conclusion.
Marty
