If you are able to make any changes in the room by adding (record) bookcases on one of the 14' lengths, the room should "see" itself as 13' x 14' x 8'. That could be helpful. As far as the speakers, I had WATTS from '86 to '93. Unless you have a cut with deep bass in them, the room will support the speakers. Remember that, if you listen to vocals - and one ones from current times, which add reverb, sound effects and bass to the mix, and you listen to older singers (Ella, Sarah, or whomever), there is no "mixing" in their voices (they wouldn't allow it!) and so you'll be listening to unprocessed jazz singers. The room will do find.
If you listen to things like "The Patriot Games" soundtrack, it might overwhelm your room.
I once put my system in the basement, which, although the ceiling is only 7 1/2' high, by putting insulation in between the joists, it made the ceiling seem "invisible" to the speakers (also absorbed bass running along the ceiling) and since the room was the length of that house (25 x 45), the sound was pretty dazzling. Room size counts, or as we like to say, "Size DOES matter." But only for reflections, not size itself. Remember, HP originally reviewed in a room that was 12' x 16' - and he had the IRS speakers!