Great information here- thank you for the detailed responses. I have always admired the B5 S4. It would be hard to find one with low mileage in great condition. B8 S4's are all over the place, but the prices seem to vary even for similar cars, and most of the used ones are at small-time/second-hand car dealerships.

I was not considering the V8 S4 cars (B6 AND B7, I think?) at all. We live at elevation and appreciate/enjoy having boost. I thought the RS4 might be so special that it was worth considering, despite being normally aspirated.

My wife loves the handling, 6spd, and interior quality/amenities in the A4 (it is a loaded model). I am sure if I put in an APR tune it would be all the power that she would ever need in her winter commuter, but I don't really want another modified car as we already have several, and it still won't be a power band that I find satisfying for the times when I drive the car.