I found the stock suspension on my S2R800 a bit soft for my size but didn't want to spend big bucks on a fork swap. My dealer installed a heavier set of Race Tech springs and I have found the bike much more planted on the road.
AFAIK there is no listing on the Race Tech site for an S2R800 but I do know that my dealer installed part no. FRSP S3732 springs. They are supposed to be for a Showa fork ('01 Ducati Monster 900) and not the Marzocchi but I've done over 6000 kms on mine and I haven't turned into a pumpkin yet.
This little spring rate calculator is kind of interesting too:
http://www.racetech.com/evalving/SpringRateCalculation/dirtspring.asp?brand=Ducati&yr=00-01&ml=900 Monster&formuse=form1&SpringType=Fork