I wish I had a hundred bucks, I'd jump on that. I only ever bought season 1, and it's the phat.
I actually went back and started watching them again the other day, though... man, that show does not hold up as well you would think. I remember it being so fantastic, but after the years have passed and I've experienced shows like Battlestar Galactica and Lost... eesh. I still love it, though.