If you want a smoother ride, Boge Gas Turbo shocks/struts are great (there are a few other brands about the same - but NOT Bilstein HD). Might also get (if the car does not already have them) 15" wheels (These were standard on my 1999 V70 GLT). Less rubber between the wheels and the road, as with 16" and 17" wheels, means firmer, harsher ride. I really like the Michelin MV4 Plus tires. I've have them on my current Volvo (second set), and have had them in the past on an 850 and a VW Passat. Great tire with excellent wet and dry capabilities. A little expensive though at $120/130. Dunlap A2 Sports are also good, I tried them once, but will not last long.

Be advised that my comments are for those who want a great but not too firm/harsh ride and still with excellent handling. Those who want real performance cornering, etc., would have other recommendations.