I love how this ancient thread gets revived just as I'm making my final decisions on a summer wheel/tire setup.
I understand and appreciate the fact that tire weight matters more than wheel weight when rotational inertia is the focus. But let's not forget that wheels and tires are unsprung weight and that they accelerate in vertical directions as well. Reducing the overall weight of the wheel/tire combination is going to make the car feel sprightlier and should also improve its ability to respond to the bumps and dips encountered in everyday driving.
If anyone is interested I am going with Mugen RnR's 15x6.5 +45 offset, 10.5lbs. each -- about 5lbs. per corner less than stock. Tires (probably) Michelin Pilot Exaltos, 195/55 15, 18lbs. each -- same as the stockers according to Tire Rack.
I'm hoping for a nimbler feel, livelier acceleration, and maybe even a bit better gas mileage; but to be honest the thing I'm most looking forward to is finally getting those awful Dunlops off the car.