preferably Canadian if possible, but it doesn't matter.
I have no affliation with them... but I really like Backcountry.com (Dogfunk.com is the same company with different branding). Pretty good selection, free shipping on most orders, and most importantly... very very easy returns if you don't like what you bought. I particularly like the no hassle warranty returns (you just go to the website > order history > return) and they give you a pre-paid label to slap onto the box and rest happens automatically. No weeks long back and forth on the phone/emails with photos before they accept the warrant return.
They ship to Canada for most brands (some brands don't allow them to sell to Canada :P)
Both Alternative and Empire have actual retail locations.
Empire is very involved in the local scene. It's actually my local shop. I try to shop there as much as possible.
Since they don't carry NS, I've had good luck with the Boardroom in Vancouver and Alter Ego in Winnipeg.
No insult to those two, I know that they've got a local presence too, and if I lived around them I'd shop there first. I try to give the guys near me in Toronto a chance, if they don't have it in stock then I go online.