2014 Audi A6 3.0T vs S6 4.0T

[Olivero]

I am in need of a fast barge for a new commute. 90 miles each way, some horrible roads and potholes you could lose a smaller car in, but not too much traffic most of the way. I have always got on well in VAG stuff having had a Golf, Touareg and vintage Beetle. Of the Audis I have driven recently, the Q5 and A4 were ok but both a little on the small side. The A7/S7 looks fantastic but not sure it really offers anything over the A6/S6. The A8/S8 is just too big. I know I should want an RS6 but quite honestly, prefer a discreet look.

2014 Audi A6 3.0T - 310 hp and 325 lb-ft
2014 Audi S6 4.0T - 420 hp and 406 lb-ft

My choice comes down to A6 or S6. Is the extra cost worth it?
Anything obvious to look out for in either model?

[Gio G]

Loved my old A6 3.0TSFI, but they are very rare beasts these days. I assume quite a saving on fuel vs 4.0T, unless that has COD..

G