I don’t which Bilstein models are available to fit your car. If you prefer stiff then the Bilstein HD might be a good choice. Some here on the BB have complained about them being too stiff. However, they might work well with your heavier than stock engine and rear Bilsteins. In the past, there was also
a softer touring model available.

Koni is in some ways a better choice as they are adjustable. Koni also used to have a lifetime warranty. Don’t know if that is still applicable??

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Will I buy another Volvo??? We'll see....