I would suspect your current alloys will be either et43 or et45 or very close as the B7 uses several offsets around those sizes.
ET35 is better as it moves the wheel out a bit more so you see less wheel arch gap, but ET35 is more common in aftermarket 9 spoke 18" rims than OEM , but then you'll pay a premium price for OEM alloys anyway.
They are nice rims , I've had 18" fitted to my avant and 19" , really like 20" but tyres and fitment can be problematic .
Its all down to personal preference really but I found the 9 spoke design looked much better in 19" and 20" as the tyre side wall profile will be lower and the spokes look thinner , but hey all down to personal choice.
The 9 spoke rims you have in this picture are RS6 OEM 18" x 8.5j ET30
also just keep in mind not all the 18" 9 spoke alloys are the same pattern , some have a groove full length on the spoke edges and some only have it half way and its not specific to oem or aftermarket either as both can vary.
Aftermarket rims can be in 5x112 pcd or 5x100 pcd , even multifit 5x100/5x112 pcd , oem only come in 5x112pcd or 5x100 pcd, it's all down to offset really the lower the offset the less likely they will fit without issues.
But as its B7 you'll need 5x112 pcd or multifit option .
On an 8j an ET35 will be a good option , an 8.5j on an ET35 better still , but if you start getting below ET33 on either width rim you can run into issues with bodywork contact .
Or , if you're not fussed about the stance you could stick with et43 /45 etc but stear away from going beyond ET48 or you'll have issues and may need spacers, so kinda going in a circle with them.