I was wondering how much should I offer for:

Price
$21,000

Body Style Coupe
Mileage 14,236
Exterior Color Red
Engine Rotary Engine
Transmission 6 Speed Manual
Drive Type 2 wheel drive - rear
Fuel Type Gasoline
Doors Two Door
VIN JM1FE173950146406

Seller's Comments
2005 MAZDA RX8, 14236 miles, perfect cond, 6spd, never driven in rain, new baby need to sale, call me lets make a deal $21000 405-623-0454

http://www.autotrader.com/fyc/vdp.js...ce=&cardist=64

Well there is also a white one for same price but with only 6000 miles...(but I want a red one with black/red interior)

http://www.autotrader.com/fyc/vdp.js...ice=&cardist=8

18,500 if it's a Touring

$19,300 if it's a Grand Touring

that's assuming it doesn't have NAV. If it does, then another $650-700.

Not saying you will get it for that, but it's a good place to start. Those prices are based on NADA Trade-In Value plus $700. The fact is that dealer don't use the the Trade-In value when buying cars, they go by Loan value which is 10% below Trade-In. If the dealer bought it "Right" they should be able to sell it you for close to that and still make a little bit.