So I have a '09 A6 C6 - facelift - 2.7 TDI

I want to upgrade the wheels and found these already fitted with summer tyres.


Seller says they are Q5 wheels although they are already fitted with good 255/35/19 tires so they must have been previously fitted to a saloon I'm guessing.
I also found that the regular S6 19s for this exact model were in fact ET48 ...I can't seem to find these. Could they be replicas - seller says they are original.
Now I'm running the stock suspension ( with stock 18 ET42 wheels ) but that's pretty high for my liking and so I want to go for the Eibach ProKit springs when the summer kicks in so -30mm on both front and back.
Would these create any issues considering they are 9J ? Also being ET52, should I worry about inside rubbing ?
Would they look good or a bit too "inside" ? I wouldn't want to go at the hassle of fitting spacers.
I will be using the 255s already fitted, I know a lot of you guys are running 265s on 19s ...
I found that the oem size for the 19s on the S6 is 265/35/19 9J/ET52 - is this correct ?

Thanks