Do pure copper banana plugs make a difference in the quality of the speaker sound.

I wonder if they have done significant blind testing?

I would also be curious to know if I were blind tested to compare speaker cables if I would hear a significant difference?  I doubt someone would sit down to listen to a system and say this sounds like you are using Tera Labs or Kimber Cable.  I do think buying a decent set of cables does make sense, but not spending more than $1,000.  However, $1,000 is a lot of money.  The system should I guess cost at least $10,000 to warrant the expense.

Problem I have connecting my speaker cable to my ARCAM AVR 550 is I also have my two REL S2 SHO subwoofers connect to right and left channel using the high level connection.  So far, I am not sure I can use a spade connection based on the design of the left and right speaker connections at the back of my receiver.  I think Spades are best for a secure connection.  If anyone is familiar with my ARCAM receiver, I would appreciate your help.  My banana connections work themselves loose over a period of sever weeks and when this happens it takes me a half hour when moving my cabinet against the wall to maintain a solid connection.  I would hate to hog this discussion.  This group is extremely knowledgeable and perhaps someone is familiar with my receiver and can offer some help.