I purchase components from them (memoryexpress.com) online; and I've since advised two friends (both of whom have had PC's built by them) in Calgary to use them. So far no problems. One took a defective video card back to them and exchanged it without difficulty; I haven't had any personal experience with exchanges with them.
Quality seems fine, prices quite competitive to other Canadian suppliers. Do keep in mind that you're often (though not always) looking at a 10% or more premium over US prices for electronics. Shipping (I almost always use cheapest ground with everyone) was ok. Not as fast as NCIX or Amazon.ca, but significantly faster than Newegg.ca. (Your mileage may vary of course).
Returns can be headaches. I'd dealt for years with shoprbc.com (an Ottawa outfit that I would still rate relatively positively, though no longer as positively). I had an obviously defective hard drive -- I ran the manufacturers diags as soon as I installed it since it was making strange noises, and the manufacturer told me to take it back to the retailer. They argued very aggressively and forcefully that the drive looked fine that they'd have to put it in a queue for testing and charge me for a new one until they could confirm what I was saying. Boggle. Since I'd spent thousands there over many years, I was a bit taken aback at the very aggressive attitude. However, they were as good as their word and did indeed remove the credit card charge within a day or so.
I'd figure out what you want, and price it out at a couple of reputable suppliers. If you're lucky enough to stumble into a big sale somewhere that coincides with what you're building, that could save you a bit too.