You could look on Ebay. Might be better to sell the enlarger and light source separately. A assume it is not a variable contrast cold light heat. I think you would be lucky to get $200 total.
I can't address this one specifically, but the research I did while trying to get rid of my Omega D2V with a compliment of lenses and accessories, including Zone VI head and stabilizer, led me to believe it would be hard to get more than a couple of hundred for any enlarger these days.
The 23c II was a great enlarger. I started with one back in 1970, and it's still the most enjoyable enlarger I ever used.
It is absolutely amazing that such fine equipment is going for pennies on the dollar. I just bought a Zone VI 4x5 camera, lens, 16 film holders and a beautiful Zone VI tripod for less than a thousand dollars. It's sad in some ways, but it the flight to digital has given the serious hobbiest a chance to own equipment he could only dream about.
My Beseler 23 is a great enlarger, but I'm stepping up to an Omega D5 so that I can enlarge the new 4x5 negs.
John MacKechnie