Hmm...I've always just used an extra 1/4" cable I had laying around...never had any problems, but maybe I should switch?
yeah. if you think about how the electrons are traveling in the wire, it makes the most logical sense to have both wires the same. think about it as a radiator in your car. you have an inlet and an outlet, say its a hose of about 2.5 inches. you get a smooth even flow around the system. now take that system and replace your inlet with a 3/4 inch, and the outlet with say 50 coffee straws. as you would imagine the flow is not going to be laminar or even between the two, and your inlet flow rate (current) will be more than the 3/4 hose can carry. yeah, its a crude analogy, your car water system is 'direct current' since its flowing in one direction.. but you get a rough visual idea of whats going on.
i've seem people use instrument cables with a few hundred watts of PA gear, 100w 4x12's.. do i think a instrument cable will catch fire on your champ? no, but its the wrong tool for the job.