Yes, you are correct. It is either an A4 or S4 (probably an S4 because of the lip up front) with an RS4 grille and wheels. The front bumper is definitely an S4 bumper. The lips on the wheel wells are also not wide enough to be an RS4.
See example below:
And I'm floating in the most peculiar way.
B7 Audi A4 2.0T
Aerospace Engineering -- The University of Texas - Austin