Beautiful car, gorgeous interior.
04/05 B6 s4 avants will run you $27k-35k depending on condition, mileage, CPO, etc.
From what I’ve researched, stay away from the early 04 models (pre 10-03 build date) as they seem to have more issues.
Even if it is an extra couple grand, I recommend getting a CPO’ed car that will cover you until 100k miles. The peace of mind is worth the money when owning a 4.2 audi.
Good luck in your search.