I have been driving a 2006 C4S for the past 6 years year round (although I sold it last week), and the car handled great in the snow, with snow tires. Had a second set of rims and thus made it easy each year to swaps summers for winters and vice versa.
Andy and Wayne’s advices above are bang on and nothing to add (I used 18″ rims for winter with the exact tire sizes above; and Ernie had installed spacers on the rear wheels to ensure those rims cleared the brake callipers and struts etc.).
My one suggestion is that when you mount your winter rims, put some anti-seize on the hubs first. Otherwise with winter slop and attendant rust, they are a bugger to get off in the spring.