You're right, Craig, they're identical except that in many cases the alternative model numbers are available in silver only. This is another example of Denon's practice of using different model numbers for units which would supposedly go to a "lower" level retailer(e.g. 2805/985). Often, although the prices that you saw were the same, the alternative sells for less and a couple members here have been able to take advantage of that on Denon receivers. A little clue that that's the case in your example is the fact that the manual is labeled 1710/555. They're in the "specialty audio" section on the Denon site in their "Home Theater Series".
Here's a comparative chart of some of the models.
