No... You do not need hubcentric rings. I don't run hubcentric rings with my 6UL's. However, when you install your aftermarket wheels the lug nuts MUST be torqued down with a torque wrench to 85-90ftlbs while the wheels are still off the ground. After your first drive with the new wheels installed re-torque your lug nuts with the car on the ground and again after about 500 miles of driving.
Also your stock lug nuts may not work with 6UL's and it is highly recommended that you install new light weight lug nuts as these will allow you to get better torque on the lug nuts and more turns of the lug nuts. 949racing offers sets of their lightweight lug nuts in many colors which is what I went with.