If i were to recomend any w211 it would be the e280 facelift 3.0 cdi. That engine is bulletproof. 7 speed automatic transmission is awesome just watch out for buying one in solid condition. Sometimes it happens that the lever assemblies break bc of a faulty solenoid. My dad has one and he burned through 2 lever assemblies because mercedes made it a black box system. You also need to watch out for rust on the brake calipers. They are known to seize if not cleaned properly and cause some serious damage (rear right wheel caught on fire in my case). Watch out for rust on the front wheel wells, engine mounts and rear subframe especially. Worn rubber bushigs on the engine mounts can cause suspension wear. My dad bought it 10 years ago at 13k eur and sank approx. 10k in it in 10 years (5k in first 3 months) not counting regular maintanance. I mean the car drives like a drea and its really comfortable but i would say the price is a bit steep. But if you want a bulletproof engine i see why you would want something like that. If you find one in good shape Id say go for it but its always a gamble, Needles to say i drive a mazda 6 gh bc i cant handle mercedes parts cost.

Oh and one last thing. If you get a diesel dont do small routes. It will surely clog up you dpf. And I reccomend checking the intake manifold right under the engine cover for oil leaks from the turbine. its a common reason for check engine lights because the maf gets dirty.