Let me give some perspective. The springs helped A LITTLE on my R but not anywhere near worth $600.
$600 ST springs maybe 20% improvement.
$1500 Weller Spring and Re-valve 100% improvement. It made an entirely new machine out of my R. It is now a pleasure to drive all day and it doesn't beat me to death. It does sway a bit more (especially with the sway bar disconnected) but you just get used to it and adjust your driving.
I wound never waste any money on just springs. Save the $ and apply it to a total rebuild.
And stay away from ST unless you are a desert racer. Unless they have changed, their setup is too rough for the average rider. If you are planning to re-work your shocks, you should consider Weller Racing out west and Double E and G-Force back east and forget Shock Therapy in my opinion.