Does anyone know if weak suspension, rear or otherwise is a common problem with Outbacks? That's about the only thing I'm disappointed with on my car. In fact, I don't think I've ever bought a car that didn't initially have bottoming out problems in the back. I would think that an Outback shouldn't be having this problem, but there are at least three places on the way to work that the car consistently bottoms out. Of course this is with someone sitting in the back. Does anyone think that this is a warranty issue and if not, does anyone know of a good place to get aftermarket springs?

STRUTS!
If your car ride height is correct then the springs should be OK.
The one thing that will let your suspension bottom out is bad shocks.
Defective or worn out either.

On each corner get the car bouncing and let go at the bottom of the bounce, the car body should come up and STOP at the ride height, if it travels back down at all the Strut is bad.

Does it bottom out symmetrically? Or just one side? Check wear marks for this.
How is your tire wear? Any "scalloping" on the edges? Any "tire balance" problems, ie vibrations you cant get rid of by rebalancing the tires?

Any additional springs or coil overs may change the ride height.