We looked at the 4.6is.. lovely - they're nicely priced now that the facelift 4.8 is out but it made more sense for us to go diesel and new for our commuter as we didn't need 2 performance beemers. That said - had BMW got the finger out with the twin turbo unit then we would have had that to be fair... new spec D seems to pull nicely and return v.good. Was tempted to chip but really there's no need.
3.0D is serene - 4.6 brings different and new talents to the table. I think the sport suspension set-up is largely the same except yours will ride on 20s from what I recall which I just couldn't warrant speccing.
Have noted our interest for replacement X6 in 3yrs time - hopefully they stick to the 2-door coupe layout and offer up the bigger diesel engines to boot..
Not Estoril by any chance? the best X5 colour IMHO.