I'd say given the fact that Ducati uses different forks depending on model, trim level (Sport vs. Supersport) and engine size, that it may be better to contact whoever you are planning to buy them from with the specifics of your bike.

I haven't tried aftermarket springs so I can't comment on what works better. I have the stock springs. The only thing I did to my forks is change the fork oil. I switched to 5W, and there was a decent improvement in plushness.