How do I price used speakers? (Nautilus 800)

I looked everywhere, and have not found a used price for B&W Nautilus 800’s. These are original owner, excellent,  and 2006 models. Can someone point me in the right direction as to what potential pricing could be for this series of B&W speakers? I looked within Audiogon, UsAudiomart, and craigslist to no avail. Getting ready to sell or trade in and want to know what my bargaining power is. Thanks in advance. 

PS. I will list in Audiogon when I get a good estimate.