The Guides like KBB, NADA Black Book and Edmunds are a good place to start but remember that they’re just “Guides”, based on varying sources of information. Even more important to the value is the Condition and “Outstanding” generally means a car that looks, feels and drives like a new car sitting on the dealers lot.
i.e. Professionally detailed inside and out, absolutely no dirt, scratches or dings, meticulous dealer maintenance records, State inspected and ready to go. The car is 8 years old so do you have new name brand tires on it? If not, it’s not “Outstanding”.
Once you’ve got it in the correct category it really comes down to how long you want to wait to get your price?
In the Luxury segment, my experience has been that anything with a BMW / MB tag goes quickly, followed by Accura / Inifinity / Lexus, with Cadillac / Lincoln / Genesis bringing up the rear so you’ll probably be waiting for a while for that buyer who’s willing to pay top dollar for your particular Cadillac CTS.
As far as your selling strategy, it’s a personal decision depending on how long you want to wait to sell and how much effort you’re willing to make?
For a Used Car dealer, dealing with the public, answering phone calls, showing cars and advertising are just part of the job so they can wait for their price but for most Owner sales it’s a different story.
But on the plus side, unlike the Dealer, all you need is one buyer so good luck.