Zonker-
I'm sure you found this info as well but....
You can buy the newest Silver line (Silver 6) at Crutchfield for $750/speaker. $1500 for the pair. Factor in that these are a model or two older and have been used then offer what you feel is respectable. If I were selling, I probably wouldn't want less than $1000 for them but wanting and getting are always two different things. Obviously discount the "I found these at GW for $40" stories as that's an anomaly, not a reality for most. Good luck on the hunt and hopefully someone else weighs in.
Edit- Unless that camera has the wrong date, those speakers are nearly 10 years old. I wouldn't think that $1000 or less would be unreasonable. Perhaps $800 as a starting point and work your way to the middle?