OP Don't let the Audi dealer give you the no discount crap. If you really are interested in the S6 then go to Audizine and ask what the guys are paying there and what kind of discounts they are getting. Then ask for a dealer referral. When I bought my Audi they told me the same thing then when I made the offer and demanded $500-1000 above invoice and they said no I then walked out. They called me back within a week and deal was done. Go also at the end of the month when qoutas have to be met.
Good luck with whatever car you end up with. Can't lose with either one.