On the basis that an electric car is not an option and you need good towing performance as well as quiet, we would suggest looking at a used Mercedes-Benz E-Class. As well as the saloon there's a cavernous estate option if you need the extra space, and both the petrol and diesel engine options are refined, especially in the case of the six-cylinder units, and the E450d with four-wheel-drive can tow up to 2,100kg.