just to muddy the waters a little, if you are doing a few miles then consider a 1.6, it maybe the better car for you...why?
...they have very long legs for motorway work from memory 70mph @3k rpm with a redline of 7k, they have the sweetest balanced smoothest engine of any 156 it is a proper jewel, and still pump's out some 120bhp, they are the lightest engine and this makes the handling an even bigger delight and the 1.6 return's decent fuel consumption too.
....they are quite rare, but they are out there, a 156 1.6TS Veloce with electric sportpack seats in metallic black (Cosmo blue/Mezzenotte black), silver or Evo red metallic make's a very nice 'keeper' indeed...it's the only 156 we have kept as a daily smoker and I sell all flavours.
Sure, the 2.0 is a little quicker but unless you are flat all the time (and in the real world who is?) you won't really notice the extra 400cc, but you will notice the lower thirst
Buying any Alfa is black or white:
a/ very nice owners who cherish their cars, period
b/ you meet complete idiots who just run them into the ground
There is some great advice here in this thread but I would just like to remind you that unless you really know your cars, but can still accept that you may need to budget for a big expense such as gearbox, clutch, engine etc then avoid auctions....are you ready to buy a car without a test drive and only seeing the car driving at 5mph
...........it's a gamble and like any gamble you need to accept you can't win them all and may loose the first one....also, contrary to what you may hear most cars make 'over book' at auction and Alfa's surprisingly often make far more than book value, they are very good sellers and the trade aren't stupid...well most aren't!
Also, don't worry, a good, well maintained 156 is in most respects a very well built car..afterall they all go wrong eventually and the parts prices are too bad at all, and in may cases quite cheap.....honestly I get far more issues with Merc's (rust/chassis/electrics etc), Beemers (bad engine's) and Ford's (bodyparts/chassis) than any proper Alfa's we see.
hope this helps, good luck, hey, one thing is for sure, any good Alfa makes any journey an event, there really is something very special about them