Is High End Cable Really Worth It and What Brand

Hello. My system is almost complete. I'm just waiting for the Dynaudio Center to arrive and my McIntosh AV system will be up and running. The dealer wants me to change out my speaker cable (which I paid a lot for), claiming I will get much better performance out of the dynaudio speakers. The cable I bought (from another dealer) was expensive, but not by the standards of what I'm being told I need. Any advice here would be most appreciated. Is it worth $500.00 of cable? I don't want to have things just for the concept. I will pay if the results are real. I just don't know. Thanks for your advice.