S4's aren't too bad service cost wise, not for a car of that type anyway. If turbos go it is an engine out job which is a fucker.
It's a lot of car and they can be had from £4k. WOuld rather spend some more and get something that's been loved and had some cash spent on the right bits. Think Martyn on here has a silver one with not a million miles shy of the 500bhp mark