All Harmony models will control the equipment just fine - they all share the same component database. The differences are in the buttons (number, type, layout), LCD screen (color, size) and battery (regular vs. rechargeable). Some models (like the 659, 680...) have a Sound and Picture buttons which are shortcuts to the Sound and Display devices used by an activity with their own separate button configuration. This thread as lots of pictures to help you decide: [Link: remotecentral.com]