OK, found the MT A6 test, 4.8 0-60, that is a 4 tenths of a second quicker, but if you look at Q mile times the Genesis has narrowed the gap to 3 tenths with a slightly higher trap seed than the A6, so it's catching up. Of course all this is dependent on track and weather conditions. At the end of the day 3 or 4 tenths isn't going to really matter unless your into street or drag racing IMHO.
An E550 is over 75K when optioned to Genesis 5.0 ultimate level, not a contender at that price point, add in Mercedes high service costs and the Genesis looks even more attractive. The 15 Genesis is a value proposition with very good build quality, my wife has a Mercedes and I have spent a fair amount of time looking over E , CLS , and S class at the dealership. I then went to a Hyundai dealer when I heard about the new Genesis and was very impressed with the build quality, the finish of some interior materials may be slightly less than MB or Audi but the over all car is very impressive. At the 50-55K price point I don't see anything that can even come close in this size catagory. Plus I was offered 2K off msrp..