...THis is the dilema.
You need to shop the car out and find it's wholesale value. I suspect that the $17K figure is probably what you'll see mostly, but you never know. Someone might have a good offer and you might luck out and sell it quickly.
Selling privately works well if you have a Civic or Accord, Camry or Rav4, etc. People watch for those models and you'll have calls like crazy. An Audi? Tougher sell. People will be scared concerning repair costs and with it out of the comprehensive warranty, that won't help.
On the other hand, it is a near-luxury car and there is a strong group of people that won't drop $40K on a new one, but $20K-ish for a nearly-new one? They are out there.
One last thing. If you're bailing on the Audi to save money, you're going the wrong way. That car has seen a massive depreciation in the last four years (as you're seeing) and it's got tons of driving left. The only way to bail on it and not eat your shorts big time is to buy a Civic/Corolla/Mazda3 as they have high resale and in three years will actually be worth more than your to-be-seven-year-old Audi. Pretty much any other make/models and you'll be just digging a bigger depreciation hole.
And advertisment has one "d" not two, so it's ads, not adds. Adds is addition, not advertising.