which car should i be looking for?

hi there, I am looking at buying another audi can any one recommend a vehicle to go for and any to give a miss ?

I will be looking at cars around 4000 to 5000 mark so obviously not a new one lol a b7 or b8 not to bothered if avant or saloon its the engines and gear boxes I am in two minds about the cars I have been looking at 2.0lt tdi s lines and 3.0lt s lines ( Quattro ) in either would be nice, I think the diesel cars would be best where mpg are concerned.

can anyone advise me on which engine and gear box to go for so for I have seen advertised 1.9lt 2.0lt 2.5lt and 3.0lt in manual gearing or auto triptronic and so on I am no mechanic so don't really know if there are certain models that are better than others if you see what I mean.

the criteria is a car that has a good turn of speed when needed, can handle a bendy a road without having to spend money on upgrading things and not having to be at the fuel pumps every five minuets lol or am I just asking to much of this model audi

looking forward to peoples views ?

cheers kev.