Sorry to dig up an old thread, but, FWIW, I bought one of these to power on/off an old Denon PMA-750 (no remote, no standby mode). I would leave the power button turned on, and control it all via the Wemo.
Seemed to work well, once I trained myself to ignore the high frequency 'pap!' sound blasting through the speakers when it turned off (the Wemo itself makes an audible click when it turns on/off, and it sounded like an amplified version of that).
However, now I'm kind of lamenting that I did convince myself that it would be ok, as my left speaker now crackles at lower frequencies, and my right channel (sometimes the left) doesn't always work when I first turn the amp on unless I flick back and forth the volume knob a few times.
It might just be me, but the music doesn't seem as loud these days, either.
Now, I can't be sure that either the speaker, nor the silent channel, problem occurred only after I started using the Wemo, or that the Wemo caused the problems, but it seems possible to me.
What are your thoughts? Am I a fool for using it, despite the 'pap!' noise?