In the bang-for-the-buck department, speakers made by Ontario companies like PSB, Paradigm and Axiom (some production may have been outsourced) usually do pretty well.

Speakers are the no. 1 source of distortion in sound reproduction, and so we haven't exhausted the technological solution space. However, at close range and (relatively) low volumes, you can do a pretty damn good speaker with just good construction techniques, proven designs, high quality components and some R&D. That's why you see a lot of companies concentrating on 2-3 way bookshelves and floorstanders with simple bass reflex subs.

Things get more interesting when you're trying to go really loud and cover a wide audience, or when you go all out.

Interesting speakers:

Danley Sound Labs [1] with their tapped horn subwoofer and their "synergy" horn speakers that have slot-loaded mid- and low- range speakers. They do insane stuff like the TH812, with 8 12-inch speakers, that weighs 584 lbs.

JTR speakers are best known for their "growler" [2], an 88-pound sub with huge output for its size.

Meyer Sound [3] speakers are very expensive, but they do some mad stuff like the X-10 with a servo-controller woofer.

Fulcrum Acoustic [4] uses DSP to correct problems with horn-loaded speakers.

[1]: http://www.danleysoundlabs.com/

[2]: http://jtrspeakers.com/portable/growler/

[3]: http://www.meyersound.com/product/x-10/

[4]: http://www.fulcrum-acoustic.com/technologies/whitepapers.htm...