No_regrets -- I've just not had a lot of success with Harbeth in my room. They always sound great to me at shows but somehow disappointing at home. I'm stuck in a purgatory of wanting their rich warmth and also wanting clarity, edge definition and transparency to the source. I completely understand the people that scratch their heads about Harbeths (see the 10Audio review) and I also completely understand those who love them.
The P3ESR's are not my primary speaker, which is a much larger Dunlavy, but I bought them because I kept hear such great things about them from sources I trust. This is the first of the latest-generation Harbeths I have owned and it may be that the magic is a result of Alan Shaw's most recent crossover efforts.He would probably deny that, I don't know. I also tend to like sealed boxes and this is the only such Harbeth, though I did once have the earlier version of this model. (But this one has the RADIAL driver, which is key.) In the midrage, they just serve up a tactile "humanity" that really floats my boat. No guarantee it will do the same for you.
Should work fine in your small room although I don't know what issues your room's square dimension might introduce. In my room (17 x 23) they do present a comparatively miniature perspective, but (1) I have not optimized their placement at all and (2) I'm fine with that anyway. I think the other Harbeth models go bigger in this respect (from memory), but as I say, these are my favorites.
Where are you located?
Dan