20% is probably not terribly unreasonable. Being a seller myself, I can understand the sellers point of view here. It's exteremely irritating to get many low ball offers in a row. For example, I had speakers listed at 825 for the pair plus shipping. Someone wrote me and said they would give me 500 shipped to their area. I noticed a lot of people don't do research before they make offers. Look at other units similar to what you want and see what they are going for. Then consider an offer.
