You could put banana jacks on each wire (one per wire, they're single conductor) and plug those into a compatible amplifier; but it would have to accept bananas. There's no advantage other than the convenience of being able to plug and unplug the wires more easily. Bare wire is "best" in terms of conductivity, and if you've got an amplifier with binding posts, probably also the best in terms of physical security (banana plugs can be pulled out very easily; I'd avoid pins and spades to be quite honest with you).
If you're using a modern AVR or something else that has bass management and other EQ/processing - you'll need to disable and bypass all of that (you want a full range 20-20k stereo signal, nothing else). I would also preference amplifiers able to deliver at least 50wpc, but that isn't to say lesser amplifiers are not suitable.
Needless to say, do all of this with all of the equipment off.
If there's a GND post on the Stax box (there should be) and a GND post on the amplifier device, run a lead between those two as well.
As far as +/- being incorrect; they would be completely out of phase. There would still be a signal, just the inverse of what the source produces. They would likely lack bass and sound very "large." It would not damage anything.
