From my experience, the Conti3s you have are close to as good as it gets, in terms of ride. Wear also affects ride - for the worse. Mich PS2s are probably as good as it gets, but I don't think you'll notice much difference compared to full-tread Conti3s. Tire pressure also has a big effect, so I'd check it. Beyond that, assuming stock springs - All Caymans ride like the sports cars they are.