Most impressive small footprint speaker

Do you have an "unlimited budget?"  If not what is the purpose of this exercise?  Regardless "most impressive" is a personal judgement. 

WaveTouch Audio Grand Teton or Antero - the equal of the best out there at a bargain price.

Proac Response D2 - truly magical / majestic / holographic sound with the right tube amplifier (e.g. Line Magnetic 518ia, etc.).

Legacy Audio Calibre - phenomenal resolution, sound quality and soundstage.

Gamut RS3i - as good as it gets... but... at a price.

Any of these when coupled with the right electronics will equal or beat any of those offered by AudioTroy

 It is whatever sounds good to your ears with you system. Bang for the buck....Harbeth 30.1.

I recently picked up a used pair of Spendor S3/5's. In my small 13x9 listening room they are absolutely addictive. They disappear,throw a wonderful 3D soundstage. Way better bass than I would have ever thought reading their specs. 

Harbeth P3ESR – outstanding.

Monitor Audio Studio,
and Proac Loudspeakers are very dynamic as well as musical as in natural sounding. Excellent value per dollar I own both after a Lot of comparison testing  .

DeVore Gibbon 3XL

GamuT Rs3iLarsen 9

Diapason 

Boenicke. 

You should check out Spendor. They make outstanding floorstanders with a small footprint. I have owned them and always found them very enjoyable!
https://www.spendoraudio.com/

Yes, I do have a pair of Rogers LS3/5a's 11 ohms (39269A, 39269B). 

Falcon LS3/5a is the most faithful reproduction of the original BBC mini-monitor. Stands required, of course! Read Art Dudley's review of it and several others in a recent Stereophile. A true desert island speaker!

Actually no we sell many on that list and have heard the others.

There is no best here lots of good choices

Audiotroy, all you've done is list a bunch of speakers in order of price and assumed without good reason that the performance varies in the same order. 

This is a bizzare post, you talk about size as well as possible cost no object, Some of the uber high end loudspeakers which are stand mounts are small but not necessarily as tiny as lets say a Proac tablette.

So if we were to create a list based on price ranges:

Class A:

Boretensen
Radiho
Tad ME1
Vimberg Amea, (haven’t heard this model but heard other Vimbergs)
Other similar compact exotics with very high end drivers

Class B:

Kef Ref 1
Focal Sopra 1
Paradigm Persona B
Dynaudio C1
Joseph Audio

Class C:

ATC SCM 19
Harbeth Compact 7
Proac
PMC

Class D:

Kef R
Quad Z2
Dynaudio
Proac Tablettes
Dali Mentor Minuet

Class E:

Dali Oberon
Kef LS 50
Quad S2
Paradigm Premier
PSB Imagine Mini

Dave and Troy
Audio Doctor

Joseph Audio Perspective.

It's known for being a "holy cow I can't believe that sound is coming out of that little foor-stander" speaker.