20s will fit. they look great if you lower the car. so long as you have a decently high offset youll be fine and shouldnt have to worry too much about rubbing. i ran some 19s and rubbed pretty bad in the back until i rolled the fenders. it took me all of an hour with a mallet and heat gun.

everyone will say 18s look "better' but the best looking cars in the world have big, tucked rims.

as far as springs, depends on how low you want to go. an inch or four inches?