You can use the blue book, and you can see prices on completed ebay listings. I owned 803s, and kept track of the prices often. I think you'll find the 803s (or 803S) are worth between 2500 and 3000, and the 804s are worth 1700 to 2200. That's my estimate, which is worth about as much as you paid for my thoughts. :-)
Original boxes and packaging are critical. Truly good condition is also critical to get the best price, obviously. Take a lot of pictures to document the condition. Also, they are hard to ship, so take more pictures as you pack them to ship, so you have an accurate record of the condition before shipping.
Original boxes and packaging are critical. Truly good condition is also critical to get the best price, obviously. Take a lot of pictures to document the condition. Also, they are hard to ship, so take more pictures as you pack them to ship, so you have an accurate record of the condition before shipping.