Well (unsurprisingly) I'd vote for the Passat 2.8 Syncro.
Those out there (and there's a steady trickle through Fleabay) have generally been looked after. There's the odd one that hasn't, but you can walk away from those pretty easy. I found a 60k one, straight as a die about 18 months ago. In the end my boss bought it and loves it to pieces. The transmission's basically Audi 100 Quattro, so you can't go far wrong and f*ck me do they go and stick to the road like sh*t to a blanket!
Even the 4Mo TDI Passats are coming down bloody fast now. We have one and it's a total gem and stays around 40MPG, even though we treat it mean.