I sold my 04 tdi s-line and I got more money for that than the same spec/age/milage cars with the 3.2 engine in them at that time, it is a funny combo, if they had given it the S badge it would hold up far better.
Bigger engined cars (read thirsty) tend to loose more money in the first 4 years but then they seem to hold there money better than the smaller (read more ecenomical) cars.
Only options that mean anything are, leather, wheels, upgraded stereo and sat-nav, I don't care what anyone says, the last 4 cars I have sold have had nav and it has added £1000-1500 to all of them and made them sell nice and quick too.