Very nice bike. I've admired the Soma brand. They ten to use Tange Prestige tubing, which is high quality. I bet it is a great rider. Sadly, in these times it probably isn't going to fetch anywhere near $800, even if arguments can be made that replacing it for that is impossible. That's always been the "catch 22" in my opinion.
Good luck!
Edit: And, check out the recommendations from knowledgeable, experienced people like wrk101 here, who will explain how they maximize their return on investment. Good photos are crucial and making sure bar tape is in great shape are a start. Make it to where the consumer doesn't have to do anything to the bike in order to ride it. Leave loose ends and they'll pull them and ask you to lower your price.