I'm very happy with the spec on mine, it's a 2012 facelift. Fully loaded except for B&O sound and Sports rear diff.
Personally, I think the 19in wheels make the car look a lot better on the road so I'd have those.
The standard seats are good but full leather super-sports are a different league, they feel a lot more up market and are very, very comfortable as well as supportive.
I use Drive Select a fair bit as I've got a family so I change it out of dynamic whenever the kids are in the car - I guess it's not a must but it's a nice toy to have and really does give you 2 cars in 2.
S-Tronic - must.
Tech Pack High (HDD Nav 3G) - must. The full infotainment system and the ability to store music etc on the disk is wonderful. It runs the nav off the HDD and it's a pretty good system, if you have ADS and MMI it's all fully integrated.
I didn't bother with B&O sound as I thought that the standard system was good enough for my ears.
I didn't bother with the sports rear diff as (from what I've heard) it only makes and different, or is noticeable, if you are tonking it and on the edge of the handling. 99% of my drives are about with the family, to the shops or to work so it's not something I would ever get the use out of.
It's a tough find to get the spec you want, in the right colour and right mileage....for the right price. Good luck.