And
that's why you should buy Project Gotham 2 on the Xbox.
That's got the Enzo, F50, F40, 288 GTO, 360 Modena, 360 Spider, 360 Challenge Stradale, 550 Barchetta, 575m Maranello, 250 GT, 275 GTB, 355 F1, Dino 245 GT and Testarossa. All the Porsches are in there too, plus the TVRs, Pagani, Koenigsegg, Lotus, Noble, Ascari and Saleen. AND you can take any one of them round the Nordshleife. Woo!
Although it doesn't have the massive number of cars that any of the GT games do, it actually has the ones you want i.e. not Mazda Demios.
On a side note, I can't remember how exactly he did it, but my friend got the Escudo to go over 600mph on the speed ring on GT3. I didn't believe him when he told me, but he did show me... And you call that game realistic!?!?