Where are you looking to have this info displayed? If it's on the remote itself (like on the LCD of a Pronto, that sort of thing), I don't see how that would be possible. The only example that I know like that are the high-end Sony AV receivers that come with an OEM remote that displays that sort of info, this is possible because the remote and the receiver communicate with each other using IR signals. So, I guess option 1 would be to replace the Marantz with a high-end Sony.

A low-tech solution might be to split the AV out from the receiver into two, with one end going to your current TV and the other end going to a small (maybe B&W) TV set that is not enclosed in the armoir. You would only use this small TV when the armoir is closed.