Key safety point: get some heat-shrink tube big enough to fit over the end of the 1/4" plug if it is metal. On "all" bridged amps and many Class-D amps, the sleeve, and the backshell if it is metal, are -not- at ground potential. If it should contact something that is grounded like, for instance -you- when it is powered, Bad Things can occur.
The shell should be insulated... And never plug or unplug speakers with the amp powered.
I apologize if this sounds pedantic. I for one was not aware that the shell is not at ground and was quite surprised to learn it. I still have to find some big heatshrink to do this myself, even tho that particular cable just takes up space in my spares box just now...