Here is one more option for you. These are still available from Monroe, but are special order at most part supply houses. The price shown is for a pair, so not really too expensive.
They will raise the rear of your car about an inch or so (if it is sagging due to weak leaf springs) and ride much better than air shocks.
Just another idea to consider. They can also be returned if you are not happy with them. I would order them thru your local parts house so that shipping or returns are not an issue.
http://www.shockwarehouse.com/site/product.cfm?id=18124