Hi can you help me please, as I'm a little confused about plugs for speaker cable. I'm looking for the best possible sound. and I understand that if I use 4mm banana plugs, that will improve my sound. Firstly I'm using bare wire ends at the moment, on both sides of the cable. I'm using QED X-Tube 300 with my B&W 603's s3 speakers, and my Amp is a Yamaha RX-V640RDS. I'm looking to buy some QED X-Tube 400 with 4mm Banana plugs, will this improve the sound? I know my speakers will work with a 4mm Banana plugs, but I'm not sure about my Amp, as it says in the manual " you can use banana plug connectors, with the exception of UK & Europe models". I've looked at the speaker terminals at the back of the Amp, I can see small holes in the middle of the terminal, but I'm not sure if they are large enough to fit a 4mm plug. Thanks for any help.