I am looking to buy an S4 Avant in the next few months and was hoping I could get some buying advice please. I owned a B8 S4 previously and had issues with the gearbox having to be replaced under warranty so would like to avoid as many issues as possible. So are there any inherent flaws with the design? Any niggles I should be looking out for? Also from what I've read the Matrix headlights are a must. Add to that B&O, a set of 19's, pan roof and I'm happy.