One of the things that is huting values is the age - cars this old are not easy to finance.

Bank of America only goes back to 2006 and at the end of 2013, it'll be 2007. Too bad, too cause they are VERY GOOD to deal with!
They financed my Graphite Roadster in an out-of-state private sale at 2.64% for 60 months.

I'm working at buying another '05 and the best I can get is 6.5% for three years.
So you see, you are kinda limited to cash buyers - that makes the 'buyer pool' smaller and smaller.

Two years ago, CarMax offered $14K for my red limited roadster with 33,000 on it - I wonder what they'd offer YOU for YOURS?
I'd bet $12K or less, again, due to age and financing considerations, but it owuld be worth going to one to see.