Steering wheel vibration under moderate braking

[Chris Thorp]

Patient is a '95 A6 quattro.  Under moderate to heavy braking, the  
steering wheel shakes.  Heaver braking = more shaking.  After a  
certain point though, very near locking the wheels up, the shaking  
goes away.  It's been getting progressively worse for about 10,000  
miles.  This just a simple warped rotor or is it something more  
seriously wrong with the frontend?  Any ideas?

-Chris