Where can I find a value of old amps


I picked up a pair of Marantz model 2 monoblocks from a estate sale. What is the resale value? I usually could find other units for sale on ebay or forums like this to get a idea of what to ask. I can't find much about these on line.

If you could point me towards a link that would help me

Thanks Joe
ssccooppee0f63
Here's a listing with price information that suggests a price range of $1580 to $2250 (each? per pair?) obviously depending on condition, but assumed to be in working order:

http://www.classicaudio.com/value/mz/
Thanks for your response but when it comes to amps like the model 2's the Bluebook doesn't accurately reflect the actual selling prices.I'm trying to find some recent sales.