I would just stick to going to popeyes, the local store. They price match online sometimes if you ask, get free shit, and arnt the assholes at GNC.
I have looked around, and its really only worth buying online if you are willing to buy more than 5-6 lbs tub. In that case you can get some extra percentages..
Believe it or not though, amazon.com sometimes has good deals.
www.supplementscanada.com - popeye's online store
svncanada.com
usually the ones i check out