The cars that are the most reliable (Hondas, Toyotas, and most Subarus) don't depreciate very much. That means that buying a 2-3 year old one won't save you much money. If you get a car that tends to depreciate at a higher rate (Cadillac, most Chevy models, etc), then getting one a few years old might still let you get a deal. But you may pay later in higher maintenance.
If this is a car you plan to keep for a long time (8-10 years), at least give some thought to buying a new, reliable brand and make do without all the bells and whistles. A Honda CR-V is considered by some an SUV, but its a small one--it weighs within 150 lbs of the TDI you are looking at. You can get a brand new one for about what this dealer is asking for the several year old TDI. No funky maintenance problems, etc. And made int he US, not Mexico, if that's important.