Nah hubs will be fine. There are people that have used cupra r brakes as its a good upgrade. But I don't know who tho. It will depend if the carriers line up to the bolt holes in the hub. Also whether the calipers will sit in the right place to not catch anything. 323 discs will need 17s is of thought tho you could use 312 discs, but as I said it will depend on how the sit when mounted. That I can't help with sorry