Question about Tires and Steering Wheel

I have a few Q's: What is the diameter of the 2000 Subaru Impreza RS Sedan's steering wheel? The stock tire size is 205/55-16, I am planning on switching to 17 inches, what is the widest tire width can I use with out it interfering with my fender/wheel wells, driving, and steering. Once I get that, what would be the appropriate wheel size? 17x? I'm not planning on dropping the car 2 or more inches. Thank you!