Tires for a 2003 330ci?

I don't think the car is sport package, though it does have the movable thigh support (how else can I confirm if I do or do not have sport package?). Rear tires need replacing. They are Uniroyal 245/40ZR17 91W. Fronts, which are okay, are Michelin 245/40ZR17 91Y. Assuming the car is not sport, is it correct to have same size tires on fronts and backs? In terms of replacing the rears, I don't really want to spend the money on another pair of Michelins. So, what else should I consider that won't be so expensive? And is there any sense in putting the better Michelins on the rear and putting newer, but less expensive tires on the front?



Many thanks.

Tires for a 2003 330ci?