We have an Avant with Recaros. Two kids, one 4 and the other 18mths both have isofix car seats. Not the largest car in the world, but have not experienced the problems others have had with Bucket seats. I do have seat protectors on the back of the front seats
Nowhere near big enough in the back. I've an RS4 Avant and an 4 year old.....tiny in rear, no room for adults and I need to move seat well forward to allow acceptable (just) space. I'm 6ft.
Get the 6 series avant.