I have genius 15 x 6.5 all around. I used Yokohama S-Drives,205/50 on the rear and 185/55 on the front. They are working great - excellent grip, quick steering, reduced cross wind effect, and improved ride compliance. A side benifit is that I've maintained the OEM stager front and rear, just added 30mm width on both ends.
Several people have used 195/50 on the front, but that strays from the OEM diameter, but the 185's just came available and will work on your 5.5 front rims.
I'm also using a full Brabus suspension kit - new springs and Bilstein shocks and struts. It's made a new car.