I just got an '05 S4 and I was wondering why this motor takes 11 quarts of oil. That seems relatively high for an engine this size.

That seems high, I have a 00 A6 and my 4.2 takes like 8 or 9 Quarts.

Read the Manual. Your car only takes 9.5 quarts, no more, no less. If you put in 11.5 quarts I would immediately drain the oil and do it again. You could be ruining some of your seals.