The S4R has the 996 engine so will be similar to yours although the intake and zorst are different it sounds very powerful by all accounts
the gearing is low to i think.
The S2R has the same torque nearly as my 748s but due to the 2 valve motor has less top end but it looks less cluttered and is cheaper to.
I to am thinking of a monster next if i stay with ducati
go for the S4r I think