Remy and I pulled up next to a C6 in Maidstone about a month ago. It was the sex. I want one with every fibre of my being... even though my BX 14 is the best car in the universe. We were in one of the XMs and waved frantically at the guy who recognised we were in the "sire" of the C6, and from the way he reacted he must be a former XM owner or at least a veteran Citroenophile.
3 weeks ago in Camden we were crossing the street when all of a sudden everything went silent, and without making a noise an SM flew past us. Our jaws were on the floor and I desperately waved a Medway Citroen card after them. I still don't know how the SM managed to make Camden Town fall into total silence as it passed. True story.
TBH I'd rather spend a huge amount of money on a C6 than the C5, as the C5 is slowly becoming a very problematic car. Great news for us, but not for the owners. Don't tell on me, but I would steer clear of them

The ONLY advertising I have seen for the C6 is on the Citroen website, and I think ONE pic in the Citroenian or something crazy like that.