The measurements performed in post #1 show -3dB around ~15 degrees off axis. This is going to stay the same regardless if tested by another, or seating distance from speaker. The 1961 series is very popular (in fact Arendal discontinued it, and have since brought it back into production).
Give consideration to the Arendal 1723S Bookshelf S THX flipped on its side as a center, if compactness and vertical placement are a challenge. Not too much bigger than a horizontally placed 1961 Monitor, -3dB is ~18 degrees either direction from acoustic centerline, measures and to my ears sounds FAR better/fuller than the horizontal 1961 Monitor (I sit 6.6 feet away, and am at 0-2.0dB across my three seats). Note you will likely want to properly treat your room to tame the relatively wide vertical dispersion in this orientation (I have a thick cloud on the ceiling which really helped with the center response, vocals are crystal clear).