I too have a 14n and 760. I added a lightly used 720x a few months ago. Its a great compliment to the others...especially considering current prices. Super speed and low light performance while physical operation is almost identical to a 760. You won't have to re-learn how to navigate windows or where to find critical controls without thinking. The batteries/charger etc are interchangeable with other 7xx and 6xx cameras. I've not used a 620x but I assume its different from a 720x in much the same way that a 660 differed from a 760. I have used both of those though its been a few years since I picked up a 660. The 7xx series is compatible with just about all of the latest PhotoDesk/Camera Manager features. The color temp slider is the only thing that I can think of that doesn't work. The 6xx is not compatible with more of the newer features. It uses the older DCS file format instead of DCR. I don't think it shows a preview in Camera Manager? The menu system on the 720x LCD is pretty much identical to a 760. I seem to recall what features added to the 760 that weren't in the 660 were a better histogram and eyedropper sampling; and the zoom to one to one feature. The general layout of 7xx controls is a bit more user friendly than the 6xx series. The 760 also had a much larger buffer and higher frame rate than a 660. I think there may have been some difference in this regard between the 720x and 620x as well.