broken springs - upgrades?

So I found BOTH rear springs broken in my wagon, and I know they were new when I got the car 3 years ago. Considering I do put a good amount of weight in the car, and also drive it hard over bumpy roads all the time, I would really like to put heavier springs in there. The problem is, it's a sport package AWD wagon.

I called bavauto and they only had one set of springs that they said would work for my setup, @ $148 each. For that kind of money or maybe a little more I would love to upgrade to something a little more durable.

I know it's a shot in the dark but does anyone have suggestions or better yet experience with upgraded springs for a sport suspension-equipped wagon? Or are the rear springs even different from sport to regular? Or maybe the sport springs ARE heavier and someone put in regular springs, thus they broke? Or maybe I should not drive like a nut with a car full of skis all winter?

FFEJ I'm looking at you... your wagon driving makes me look like a granny.