If corrosion is an issue, simply twist the ends, heat them up, and solder. The plus is that there's no corrosion, and no stray strands that could blow a channel on the amp.
The beauty of banana plugs are no twisting or tightening of terminals, unless you have spring clips - then just use solder over bare twisted wire.
I've always soldered my speaker wire, whether it be bare to spring clips, or soldering straight to banana pugs.
I wouldn't worry too much about the wall plate - unless you live near a beach with salt water.