If you wanted to keep to the Mercedes-Benz brand have you looked at the CLA or CLA Shooting Brake? It's effectively an A-Class underneath but has a longer, more sleek body. It's available with some powerful engines and a panoramic sunroof came on some versions. There's also the C-Class Coupe which does have four seats but isn't as practical as the CLA. It'll be nicer to drive, though, with a rear-wheel drive chassis and better interior quality.