I think this is really what your first post should have said. I guess the question is what you plan on using the crossfire for. Is it a daily or is it something you will just keep in the garage. The warranty is great, but you won't have it very long--just about a year left on it, at most, depending on mileage. IIRC, second owners do not get the limited lifetime warranty, so I'm not sure how what affects things if you wanted an extended warranty.

I think it's really hard to for us to tell you how to go here since, really, it's a value judgement. If your car is worn out and you really lust for that new car feeling, the 08 might be a good option. Unless the car was a basket case or visually in poor shape, I would probably keep the 04. If I was going to get another vehicle, I would probably not get another crossfire. There are so many really nice cars in the world and I just couldn't see buying the same car twice. I would be looking at a last generation Z4 coupe or if I could find one, a solstice GXP coupe.

More realistically however, I would run the 04 into the ground (asusming you drive it frequently) and then buy something else later. I think the 08 would make better sense if you wanted a lower mileage car in really good shape to keep as a weekend driver to preserve the miles--it's a bit too late to do that with your 04.