If it was me, I would replace the struts and shocks with KYB assembled units and rebuild the suspension to tighten it up like new. New rubber bushings and lower ball joints. You will see a big difference afterwards since your car has 180,000 miles on it. If it still rolls over more then you like after the repairs, then install the rear sway bar that zbyers pointed you to.
To spend all the money on coilovers and not replace the rest of the suspension parts is kind of a waste. A chain is only as good as it's weakest link, and you have many suspension links that have 180,000 miles on them.