I audition speakers in stereo... I think, it is because I am, just more comfortable, with stereo. I am used to, stereo seporation of the music, having listend to stereo, most of the time, my whole life. I rarely, listen to music, in mono.
For me, auditioning speakers has to be, with my own seclection of musical CD's, too... I think, it is because, I am more comfortable with music, I am more familiar with... I know, what it is supposed to sound like. I guess it's, similar to my reasons, for listening / auditioning in stereo.
In addition, it is my habit, to audition the speakers listening to how they sound with my ears three to five inches away from the speaker for several minutes. For how speakers, fill the room with sound, I also, listen to how the speakers sound, by standing or sitting, at different vantage points around the room. I can not just listen once and that's it,... I have, to have, several different listening sessions, of the speakers - I'm serious about actually purchasing, with at least a day, in between, to finially decide. It all part of my discesion making process, i. e., thinking and carefully evaluating / reviewing, just what I heard. Then hearing it again...