Well the A4 isn't seen as it's smaller!
You have the A6 from Audi or the BMW E60 5 series, which I think you can get 525/530, that would be my personal choice.
I aren't a fan of Mercedes tbh or there engines especially the Supercharged 4 cylinder jobs, BMW have a far better engine line up.
Naturally I do exclude the AMG variants in that statement.
Martin