Arjen, I've had an idea for your "volume" dilema, but first a question. Do the devices that you want to be able to switch volume controls, use all of the menu arrow keys? Many VCR's, for example, only need an UP and DOWN arrow, they don't need the LEFT and RIGHT arrows.
If your VCR has two spare arrow keys, you could program them to work the TV's volume and program the regular volume keys to work the AMP's volume (or vice versa). That way you can chose whick volume you wish to control. This won't help you with the DVD as it does need all four arrow keys. Maybe you could look at your remote and see which buttons are un-used for both the DVD and VCR and see if any of them could be potential "alternative" volume controls.
I have a different idea for the MUTE control, but it's a bit messy. I have found that it is sometimes possible to put two commands on a single button using learning. Here's what you could try, have the original remotes for both the stereo and TV handy, then put the 15-1994 into learn mode. Press the MUTE button on the 15-1994 so that it's ready to learn (ie, the LED will flash rapidly) then press the MUTE button on the stereo's remote quickly followed by a press of the TV's MUTE button. In each case do really quick stabs of the button rather than long presses and obviously you will need to have the original remote in a head-to-head position with the 15-1994 when you are pressing the MUTE button.
If it works the MUTE button will now issue a MUTE for both the stereo and the TV, so it doesn't matter which one is controlling the volume. Theonly potential problem here is if they get out of sync (ie, the TV is in MUTE mode and the stereo isn't).
