Hey Tom,
Have you given the 15-1994 a try yet? It's true that it doesn't have as many device codes as the C7, but if it has all the codes you need I think it's better than the C7, but that's just my opinion.
As for the SLEEP button, her's how it works. If your device has a built-in sleep function, the sleep button will probably activate it. If there isn't a built-in sleep function, then the remote will substitute it's own built in sleep function. There are instructions on how to use it in both your original manual and the manuals on my site.
THere is an extra feature on the 15-1994 that isn't on the C7, which allows you to override the SLEEP button to always use the remotes sleep timer, using the 970 command.
You can't program anything to this button from theremote, but by using our hacking methods, when you create a new device code you can put whatever function you like on this button, I tend to use it for disrete OFF functions myself.
Rob.
http://www.hifi-remote.com