>>Autobahn car here is only an Opel Signum V6 Turbo with 300HP from unleaded gasoline.

I had one of those 6-speed manual 2.7T quattro A6es as my UK car in the late 1990s. More than enough in the UK with its speed limits. More recently I took a C5 3.0 diesel into Germany to enjoy the Autobahn, but as you'll know, the stretches near France are a bit lumpy and often have speed limits these days. Still good to travel legally at over 100mph, even then passed by big German machines swishing by.

>>If going for youngtimers near switching over the 30 year barrier I am thinking about a Porsche 928: not really a sports car but a GT targeting top speeds not much below my current car even if (re)designed last century, nearly totally free of old age problems like rust or plastic destructuring. If not totalled good chance it will age better than myself in the next couple of years ;-)

I have 2 buddies with older Porsches- one is the final generation of air-cooled 911 turbo that appreciates in value every year and is a blast to drive still. He's adamant that despite the steep annual maintenance, it appreciates twice as much as it costs him. Not practical to cart around 3 big dogs, unfortunately! ;-)