Sorry, for the late reply. Got home late from the concert and ended up having to work until 7 this morning. Took a 2 hour nap before having to do some gardening before it got too hot.
The Belkin will work, but is not ideal. It just adds another remote you'll need to use to power everything on. Your second link is exactly what you would need if the amp is connected to the same outlet or circuit as there will be no added benefit with the complexity of using homemade outlets with 12V trigger relays.
If you have the amp on a separate circuit and need step by step instructions on how to do it. Let me know. I need to make a couple more relay controlled outlets and I can take pictures as I make them and document it for you.