First off, I think you should keep your Goat, the reasons are endless. See KBB value below. Don't know where you live so I used my zip code for the San Francisco Bay Area. Also don't know if you have an A4 or M6, I used M6.
Hope this helps. (KEEP THE GOAT!!!)


BTW-this value does not take into account any modifications you may have done that would increase the value...
Excellent
$25,215
Good
$23,790
Fair
$21,960
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Vehicle Highlights
Mileage: 13,000
Engine: V8 6.0 Liter
Transmission: 6 Speed Manual
Drivetrain: RWD
Selected Equipment Change Equipment
Standard
Air Conditioning Cruise Control Traction Control
Power Steering AM/FM Stereo Leather
Power Windows Multi Compact Disc Dual Power Seats
Power Door Locks Dual Front Air Bags Rear Spoiler
Tilt Wheel ABS (4-Wheel) Alloy Wheels
Blue Book Private Party Value
Private Party Value is what a buyer can expect to pay when buying a used car from a private party. The Private Party Value assumes the vehicle is sold "As Is" and carries no warranty (other than the continuing factory warranty). The final sale price may vary depending on the vehicle's actual condition and local market conditions. This value may also be used to derive Fair Market Value for insurance and vehicle donation purposes.
Vehicle Condition Ratings Check Vehicle Title History Excellent
$25,215
Looks new, is in excellent mechanical condition and needs no reconditioning.
Never had any paint or body work and is free of rust.
Clean title history and will pass a smog and safety inspection.
Engine compartment is clean, with no fluid leaks and is free of any wear or visible defects.
Complete and verifiable service records.
Less than 5% of all used vehicles fall into this category