I used two of these, one for Left, Centre and Rear channels, the other for Right and Surround channels. They're cheap and work very well, but have limited (if any) protection against shorts.

Rear and Surround channels have phase inverters on their inputs and their speaker connections are reversed, to avoid any possibility of bus pumping.

I use the +15V outputs to power the speaker protection modules, and one of the +12V outputs for the cooling fan.