Depends what you mean by value - I'd say a Toyota Celica 1.8 vvti would be but thats because I'd feel more confident about its reliability potential vs the TT and I could pick up a slightly newer one with less miles for the same money. Bit more space too. A Honda S2000 would be interesting but space is not good. An older Porsche Boxster stands a better chance of being less abused than a TT. But the TT is a good looking car and if you can find a good independent to look after it it might not be overly expensive to keep on the road. Early ones had a propensity to lift off oversteer quite badly on fast bends but they changed the suspension to remove it. Otherwise normal VW parts, some reliable some not. Its cheap and easy to remap a 180bhp to 230+ bhp so that's a risk. Need cambelt and water pump changes every 4 or 5 years. Stay away from sports cars with lots of owners, people have just bought them to hack around in for a year or two and then got rid.