Anyone listen to Zu Audio's Definition Mk3?

I echo what Spirit says. While I have no experience with Zu's Canadian distributor, I have had years of experience with Sean and the rest of Zu; and they are a total class act. I first bought Def1.5s using the 60 day home trial period and have since upgraded to the Def2s and now the Def4s. Like you, I wanted to hear Zu speakers in a store first. However, the converse is that hearing speakers in a store does not tell you how they will sound at home. (I have certainly had the latter experience.) If you want to contact Zu, the best way is through their website: www.zuaudio.com

There are few dealers since Zu prefers to sell direct. However, one dealer "relatively" close to Toronto is near Buffalo:

AudioFeil International
9405 Meriul Lane
Clarence Center, NY 14032
USA
716-400-6177

Bill Feil (the proprietor of Audiofeil) was very helpful when I bought my first pair of Zu Defs. However, you need to call him in advance. Good Luck.

Ghostinthemachine, I'm based in the UK, so my advice is to email Sean Casey at Zu direct. He is a stand up guy, always prompt and super enthusiastic with replies to enquiries.
For my part I have run Def2s since 2008, and have just paid deposit to get Def4s construction up and running.
I would urge you to find a way to audition the Def4s, the Zu sound is just such an involving way to enjoy your music.