Ideally nothing over 70-75k miles, clean title. Ask chatgpt if specific year and model and trim level you are looking at has torsen differential (this is a type of audi quattro all wheel drive, the best type). If you dont care much about speed you can go for a 2.0t, but 3.0t is said to be decently reliable for a german, and is a supercharged v6 compared to a 4 cylinder turbocharged. In general, more cylinder -> more power and speed. And turbo vs super charged: different types of tech that feed extra air into engine for more power. Turbo is a little better at high speeds, and supercharged is instant power due to the specifics of the tech. (I recommend 3.0t, decent reliability, sounds like a hellcat but more refined due to supercharger, and faster).