If you want something reliable, you need to avoid Mercedes. They are exceptionally unreliable and expensive on maintenance. Even simple parts cost high dollars and require trips to specialized mechanics or the dealer. A simple strut can cost $1,000 and is computer programmed, so it is not possible to DIY as it needs to be calibrated by someone with a proprietary Mercedes programmer tool.
I'd recommend a late model Lexus IS, ES, or GS depending on your preferences. IS is the smallest and most sporty, the ES will have the softest ride at the cost of some of the performance of an IS, and the GS is the best of both worlds however you'll have to settle for more miles than you've listed (Usually around 35-45k miles). They rank very high on reliability, have great build quality (They're Toyota), and have an excellent ride. Their resale value is also very good and they hold their value well.