Audi S6 Avant (C5)

[Makem]

Hi, im needing a cheapish estate car but wanting to get something a bit more interesting. Have been looking at the C5 S6 which seem to be going for decent money at moment. All that V8 power is very tempting.
Just have a few quieries though. Are these easy to tune, not looking to do alot maybe a ecu remap, filer and exhaust.
Most of them are 100k miles mark, are they pretty bomb proof mechanically?
Also regarding the tiptronic gear box. Im not too keen on automatics generally but wondering if this works well if you want a blast on twisty roads. I know some of them can be not be that responisive.
Sny help greatly appreciated. Many thanks.