"Best" mini-monitor?

I am also constrained by a small room.  I have had the Micro Utopia BE.  It is a nice speaker but I did not feel they were very coherent in the small space.  I felt like I was listening to the tweeter.  I have had the Wilson Benesch ARCs and they great.  Easy to get in a small space.  I do see a pair of WB Trinitys on AGON now in your budget  which is like the ARC plus a super tweeter .  My current speaker , which I have had since 2012, is the Vivid Audio V1.5.  Awesome speaker which would be in your range used and your amp would drive them.  Both the WB and the Vivid are great choices. Both would not require additional cost for stands. 

Also not a mini but take a look at the Clearwave Duet 6 monitors.
I've had them for over a year now and they continue to amaze.
They're located in Rochester, NY if you're ever in the area.

All the best,
Nonoise

+ 1 glennewdick just got a pair of AN/J's love them and the AN/K's are great too you can't go wrong with either. Great with tubes too!

I have had mini monitors in my study for many years. Originally the Rogers LS3/5a (the improved 11 Ohm version, however) and more recently the far better Harbeth P3ESR. I have obviously not heard all mini monitors, but I do believe these are likely to be the best you can buy, at any price. The midrange is to die for, with a reproduction of voices that comes very close to that of my Quad electrostats in the main listening room. Imaging is similarly realistic, without any listening fatigue. Bass output is clean, and remarkable for the size. Measurement data give an equally outstanding result. I sympathise with your desire to have the very best, and your willingness to pay for that, but small speakers do not cost that much to make.
You are quite right not to go for deep bass. In a room of that size it is impossible to reproduce deep bass accurately. The Schroeder Frequency would be about 240 Hz, and below that you will have problems with room modes (and their upper harmonics at higher frequencies). In bigger rooms that Schroeder frequency would not only be rather lower, but room modes at lower frequencies are also easier to equalize because the equalization would apply over a much wider area. In your case, with equalization, you would really have to sit very still in just one position. So in a small room there is only one option, and that is not to have deep bass.
The Harbeth P3ESR is a closed system, and that has the additional advantage that it can be located a bit closer to the walls, which is a real bonus in a small room.
They do like a bit of power - in my case a 2x100 watt Quad 405-2 is not excessive in my 16x12x9 feet study. Personally I prefer solid state amplification because there is less risk of load dependent frequency response due to high output impedance. Harbeth speakers are a benign load, however. At the advice of Harbeth’s designer, I do not use any fancy cables.
These Harbeths are also interesting in medium sized rooms if combined with a subwoofer. I tried that by way of an experiment in our big living room, and with the B&W PV1d subwoofer and more powerful amplification of the main system (equalized by an Antimode 8033). The PV1d can be set up very precisely for crossover frequency and slope, and when that was done, integration was perfect and the result very impressive. In this big room the sound bubble remained a bit too small, and dynamics were a bit restrained, but that was to be expected from such a small speaker in a large space. The combination would have been perfect in a room of, say, 15x20 feet.

Try the AERIAL 5T, great monitors!