If you go gold there is a group buy for the supercharger http://www.lexusownersclub.co.uk/forum/ind...ST&f=63&t=5659& for 2500+VAT from TDi www.tdi-plc.com/is200.html
Benefits of the supercharger are more power, more torque, higher top speed (if you have an automatic), lower 0 - 60. If you want to get more power later you can get new manifolds, intake, boost upgrade etc.. If you are planning on very high HP later you may be better off getting a turbo instead but other than that well worth the money.