[user1234]

You must be talking about KBB private party value, but good luck even getting KBB trade in value from the dealership. Even so, if you're only taking a $2K-$3K hit on the value of new compared to your trade in, I'd say it's worth it cause your new car will also be worth more. The sucky part is with the interest rate, but again I feel you are too optimistic - who's giving you 4.7% now ? more like 5.5% at least. But still not a total deal breaker although I wouldn't do it just for the ipod thingy. It should be possible to get a new HU with aux input, no ?

 

[user1234]

Something else doesn't compute in your math, cause you say you paid $18600 out-the-door, I assume you mean this includes the taxes ? Is so, suppose your pre-tax sale price was about $17500 how exactly do you believe your car is now worth over $18K ? You think its value went up ?
Sure these are some idiots out there but no one will pay for a used 05 car more than the price of a new 06 car. In general cars are worth half their original retail value after 3-5 years of being used. So even best case scenario, the value of your car drops by about $2000 per year.