I have terminated many of the WE wires (same tinned copper type wire) and prefer soldered connections for the tinned wire because the tinned coating melts resulting in a more direct contact with the underlying copper.
Although some prefer no connectors, I am skeptical that the absence of connectors can be easily heard given that the speaker cables typically connect to two binding posts and the signal travels through a bunch of other solder joints in typical amplifiers and speaker cross-overs. I prefer connectors for convenience.
I like the Cardas GRS copper spades but couldn't find them in a search of vendors this morning. Another good option is to use the Cardas copper jumpers and cut off the link section resulting in two spades that you can solder directly to. Use some thick, adhesive-lined heat shrink for a stiff and well-protected connection/termination.
