Thanks Messrs XenonMan and Becker. I finally figured it out after my IQ had some time to grow. I truly (and foolishly) did not think about looking for the other commands on the additional pages as well as the pages of "favorites" on the MX-500. I think I have found all of them now (i.e. tuning up / down, select, etc), but they're not the most convenient. Still, I can always send the commands to my other MX-500 and put the commands where they most make sense, and then clone that "component" back to the other-other MX-500 - at least I think I can clone a component rather than the whole remote. Either way, it's worth doing because in the end, it will run the 1600 and the 1700 - and my girlfriend will be happy (ier?) now as she'll finally have a remote for her 1600 (I plan on giving her the other MX-500).

Thanks again guys...

[Here's an interesting update on this... Since both of you nudged me in the direction of revisiting the codes, that sort of vectored my thnking as to the best work-around; so thanks for that. I tried the various codes (of the three listed) for the MX-500 for NAD. That is, I used one MX-500 as a code-based remote control, and then in my OTHER MX-500, I set up an NAD component with the buttons (and the buttons adjacent to the LCD) labeled as I wanted them, i.e TUNR>, TUNR<, TAPE1, TAPE2, CD...etc). For each of the three NAD codes, I was able to generate some codes, and I would then teach those to the other MX-500. I did this using all three codes listed for the MX-500 (for NAD) and in the end, managed to teach every code to the other MX-500 (save for 'video').

After that, I was able to clone the custom NAD 'virtual' remote in the MX-500 back over to the MX-500 that had served as the code-based remote (the 'source' when I was teaching the codes to the other MX-500). I guess it's true: two remotes are indeed better than one. I can live with not being able to select the video input from the remote as the main inputs on the NAD's are the local streaming devices and the whole-house feed (each local Audiotron is connected to TAPE1, and the whole-house feed coming from zone 2 of the 990 is connected to TAPE2). I can switch to the tuner...select presets, scan, mute, adjust volume etc - pretty awesome as I had been using them as remote-less units. I'm really gald that I bought the MX-500's when I did. Again, thanks for keeping me focused on the fact the I had codes that could eventually get me there.]