Kennedy makes a flywheel clutch combination and a I believe Tilton makes a clutch as well. I am not sure on the S4 if you can use the Kennedy triple disc which I highly recommend if it will work. My car has about 500hp with an S4D and I have over 1500 pre run miles on it with no problems. The double disc setup is easily fried. Another option is a TCS torque converter and I believe they make a flywheel as well.
The pressure plate is Kennedy as well. You need to verify that the triple disk will work with the standard S4. I have the S4D. The torque converter setup is just like an automatic transmission has. It has no clutch and you just let off the gas and shift. This setup is easier on drive train components as it is a fluid coupling between the motor and transmission