http://www.sonystyle.com/webapp/wcs/...52921644574903
Above is the link to the Trade-in program offered by Sony. It only states trading from a 500 to a 505. Read the terms and conditions as you can only buy from Sony's online or retail store.
700 vs 505. The 700 has a few added features not found in the 505. If you have used the 505 at all you may be a little disappointed in the 700 screen contrast. If you are near a Sony store or Borders bookstore definitely check out the differences between the two devices. A Sony store should have displays of all the colors.