Reasonable price I would think would be between 9.5-10.5 depending on extras and condition. I know that the turbos don\'t like being pushed much further than stock so look out for ones with boost controllers etc.
Apart from that just the normal stuff, clutch and gearbox, check diffs and service history etc. Ive just brought an 03 GTB (had to settle for a tiptronic) and my average fuel consumption according to the computer is 8.7km/l but on the motorway it will sit around 12-14km/l