Your tire sizes are fine. If you want a softer ride the Eibachs will give you that. I took a Eibach Pro Kit off my SRT6 as I didn't think it could handle emergency maneuvering above 75 mph; Just way too much sway for me. I went back to the OEM springs. I have H&R springs, shocks and sway bars on my Limited and it rides stiff, (lowered about 1.4 inches) but I am much more comfortable driving that car at speed in curves and high speed maneuvering. There is a huge difference. So why are you lowering the car?? You have to have a definitive answer to that and then live with the consequences and if you lower it you must find a way to adjust the camber both front and rear or you will wear the inside of your tires out very quickly. The stock OEM suspension has no camber adjustment.