I have an rs6 too,
I have had the oval bezel around the stereo off many times. To get it off I have usedat various times a flat-bladed screwdriver, a 1" putty knife, wooden shim. Whatever you use, wrap the end in electrical tape so you don't scratch the plastic. I usually start on the passenger side just because that's where I sit so the steering wheel isn't in the way. Squeeze the top and bottom of the bezel slightly to make a small gap, put your putty knife (or whatever) in there and just pry up. It is only held on by clips. It once you get it started it should just pop right off. Once you have that off, there is a narrow piece across the bottom of the opening that also slides straight out to give access to the lower screws on the stereo.
I hope this helps.