Quiet and Great Dry Grip really don't go together
I don't have experience with the SP600 but the SP01 are great if you don't mind the noise and can find a set for cheap locally. *edit*Just adding comparison about the OEM tires I know the sp01 don't have the size for 18"
I'm still debating on 595RS-R or PSS as my next set if I don't find some SP01 locally
Also, I'm with everyone else.. not sure why OP doesn't seem GR and GD can be compared. Hell there is plenty 09+ wrx posts about the same exact questions....