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. ;D
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 (http://www.racetech.com/evalving/SpringRateCalculation/dirtspring.asp?brand=Ducati&yr=00-01&ml=900%20Monster&formuse=form1&SpringType=Fork)
For others looking to replace their springs, also see this thread http://ducatimonsterworldwide.org/index.php?topic=1902.msg21797#msg21797 (http://ducatimonsterworldwide.org/index.php?topic=1902.msg21797#msg21797)
Other members gave some good input on the usefulness of the Racetech rear spring calculator in particular. New springs will be my next, and probably last, serious mod.