Advice needed - what to charge for a 2006 10k Pkg 6 Prius?

Hey there, I am moving and am going to have to sell my beloved Prius. (Boy am I going to miss it). It's silver, in excellent condition (one very small, nearly invisible scratch to the rear), coming up to 10k on the odometer, package 6:

Rearview camera, JBL AM/FM stereo w/CD changer/MP3/Bluetooth/(9) speakers, Smart Key system, driver/front passenger seat-mounted side & front/rear curtain airbags, vehicle skid control, alarm system w/HomeLink, HID headlamps, front fog lamps

Would really appreciate some advice on how much my asking price should be for this level of vehicle. I've trawled the websites but there's tremendous variation with no obvious reason. I'm in Washington DC.

Thanks a lot!

Auto Trader is a good start
http://www.autotrader.com/hornav/edmunds/frame_a.jsp?restype=used

21K-23K Retail, depending on options, no navigation is figured.