Information on A8 variants appreciated

[Bushido]

Afternoon all,
I've been away a wee while now since selling my D2 A8, but have that itch that just wont go away. Having aged considerably whilst trawling every internet source and option that I can think of, common sense has prevailed - Im back to you good folks in the know!

Ok, there is method to the madness here and its not please a case of blatant indecision that needs me to do the leg work behind the scenes. So please stay with me...

I originally set about looking for a *really nice* D2 2.8 Quattro. Gets me back into the car I loved and the presence it just oooozes. That enevitably led to the climbing up the engine sizes and range. When I got to the v10 I knew I was in trouble (and that's Big Ronnie's fault - and he knows it )

The D3 diesels have suddenly become an interesting proposition to have a little remap and play. Where I'm really struggling is to find concrete information on the differences between the 4.0 and 4.2 diesel options. Also, how credible are the 3.0 variants?

In essence - I'm looking for a beautiful example that will fill my driveway, has enough get up and go to keep me happy once in a while but wont be a rain cloud hanging over my head with the fear of a brutal bill awaiting me. Budget is negotiable around 2-5k depending on the car.

Talk to me collective. You have my fullest attention