Welcome to the forum mate. What a stunning car you have bought. My favourite TBH.
Osram do a new build called the night breaker. They are a H1 build which I believe is the correct fitting for your light units. I have ordered a set of these for my van to try. They have good reviews though.
I would be cautious about putting bigger wheel tyre combinations on front and rear axle because you have a Quattro. I really would recommend keeping things the same. I think you can go to 22" wheels with your car, I have certainly seen one A5 with them. But 19-20 look the best in my opinion, each to there own though I guess.