Yeah, you can't really go putting giant stoppers up front and leave the rears alone. Ideally you want nice flat braking, rather than slamming the front valance into the tarmac when you hit them and having the back end go light.
310mm vented rears with some decent pads will be pretty awesome mated up with those RS4 brakes!
We just need to find out what exactly we need and how to do it.