I see you are in Ontario, don't know if you live near a Best Buy but they are slightly cheaper there if you have one near, they are $13 a season there. I assume the deal you are talking about is at HMV 2/$30, the Best Buy deal is slightly cheaper and you can buy S3 without having to find a 2nd DVD to add with it.
I was in the same position, never seen the show but from all the good stuff I have heard I picked up S1-3 on Boxing Day at Best Buy. It was $40 for the entire series but you really aren't losing that much if you don't like it, you could probably get quite a bit of that back on eBay if you didn't like it