I would just like to warn you that if you order from Cathe directly and not from CKSales, you will have to pay a hefty import duty. This duty will likely be more than what you will save on the presale because the duty itself is quite expensive and the post office or shipping company (UPS) will charge you a brokerage fee for collecting it! I ordered from Cathe.com before, and had to pay more than $50 in duties and fees before they would even deliver my package--this on top of the very expensive international shipping I had already paid to SNM.
I have preordered every series since the Intensities through CKSales and have been extremely happy with their service and especially the ability to circumvent Canada Customs. I read on another board (so I don't know if it's true) that Cathe/SNM want to retain exclusive rights to the presale.
If you can't preorder through CKSales, rather than preordering through SNM, I think it would still be cheaper to wait and order from CKSales once the series is released and available there. You may have to wait a few days longer to receive the DVDs and pay the regular price, but you will avoid the brokerage and customs fees (thus SAVING money in the long run), you won't have to pay until you order, and you can also check out other people's reviews before you buy.
Just my 2 cents.
Mary