I did some checking. Chrysler is currently offering about $6,500 in incentives on these cars, plus there's another $1,000 in dealer incentives, so you can buy a brand new 2013 RT for about $23k, with low finance rates, and a full warranty, all of which is going to make it tough to sell a 2008 car for $18,500, especially when financing rates are going to be a lot higher.
Looking at the auto trader dealer listings, 2008 RTs with similar mileage are listed at $10,000-$13,000, and again those are dealer prices. Private seller prices are usually a couple grand under those, but the two similar cars I'm seeing on CL down here are both at $19k, so I'm guessing those owners are using KBB numbers too.
One thing about using KBB numbers. It looks like you are using the Excellent numbers, which is what most private sellers and customers use. Most dealers use the Fair numbers because people always tend to overstate the condition of their cars. When you've seen a car for years and years, it's easy to get numb to some of the warts that are on it. Things like little chips and scratches, tire wear, holes or small defects in the upholstery, stains, etc., become invisible over time, but those are the things that someone who's buying the car, and looking to knock the price down, is going to lock in on from the start and either want fixed or get a credit for. I saw that happen a lot when I was working at a Ford dealership. One person's "there's hardly any miles on those tires" is another's "those tires are worn. I want new ones."
The other challenge you're going to have is financing. Cars with five years of age, and over 50k, can be very hard to get financed because banks have a very hard time making back the money they lend if the borrower defaults. That's why they like to make loans on new cars more than used ones. Cars like this were usually classified as cash cars at our dealership because they usually couldn't get financed at a decent rate and we would end up having to sell them to someone who could pay for them out of pocket, which meant pricing them at under $12,000 or so and selling them at $9,000 or so.
That's why I'm thinking selling your car to a dealership would likely be the best way for you to go. I don't see much chance of you getting anywhere near your asking price from a private sale, plus you're going to have to spend a ton of time talking to and meeting a lot of people who will end up with financing issues. Selling to a dealership means less money but it's a lot less hassle too.
