DO NOT stack banana plugs- pressing/pulling sideways on the end is like putting a long pipe on a wrench to increase torque. Keep the connection at the binding posts as short as possible, to prevent stressing the posts, which CAN break. Use banana lugs that have a hole in the side, where the wire enters- that is the best type WRT stress on the binding posts.
Why use 14-4 when you could just as easily use 12 ga and be done with it?