Best undiscovered speakers on the market today ?

Maybe not quite "undiscovered" but Linkwitz's Orion is an outstanding design.
No, unfortunately, I don't own a pair:)

Avantgarde Solo.

Intuitive Design Summit speakers. Almost every speaker the designer has produced, (Dale Pitcher of Essence fame) has become a legend and has been so far advanced in performance that it is common for his designs to stay current for 10 to 20 years. (not an exaggeration)

His speakers are so good that Stereophile won't review them. (politics) I can speak from a lot of experience since I have been a high end dealer for 25 years and a lot of what I carried over the years became legends.

Examples for knowledgeable audiophiles:

Acoustats with direct drive tubes
Futterman
Townsand
David Berning
Goetz
Rapparort
Black Widow
Zeta
Grahem
Marantz tubes
Dynaco
Hafler
VSP Labs
Convergence Audio (CAT)
Thore
Essence
Wadia
DCS
Celestion
Mordaunt-Short
Snell (when Peter was alive)
Electro Compienet
Hill Plasma
Dayton-Wright
Michalson & Auston
AR table
Thorens
Sound Labs
Kinergetics
Entec
New York Audio Labs
Quick Silver
Sequerra
Studer
Quad
Vanderstien
Unity Audio
NRG
Bedini
and so on ........

I second Green Mountain. Their designer, Roy Johnson is truly one of the great guys in Audio. They just sound right, I've owned many other "famous" brands of speakers and I still can't believe what my Callisto monitors can do.

I like what I've read about the Zu line of speakers - especially the Definitions but with 4 10" drivers handling the bottom end, I'd imagine that they would only thrive in a large room. The smaller Druids seem too compromised in the bass to do the trick but the fellas at Zu offer a matching sub (2- 12" drivers) and are working on a smaller version (2-10" drivers) that would better serve smaller rooms. As with all systems with powered subs, integration is key and typically quite difficult to achieve.