Well if the XF-R isn't going to "work for me" then there is always the option of something a little less powerful.

The 3L Diesel V6 looks good - one variation has the engine at 275bhp (and can be remapped to 305bhp if you desire). This engine shows something in the region of 35-40mpg which of course is a lot more sensible than the V8 petrol monster

Or do what I've done. Trade my expensive RS 5 with 15mpg average to the new S3 with 28mpg average. Performance difference is barely noticeable, noise obviously is but its a cheap, fast motor.

Worth a thought.

If you want a cheapish big car with some serious power then its got to be an old BMW 750il, I've had one and the sound of the V12 is immense