I do not use either Nordost or Wireworld but have heard both and I think they are very different cables. I suggest you stay with your current cables until you get used to your new system then try both Nordost and Wireworld. Your dealer saying Straightwire and Wireworld use the same technology covers a lot of ground. You need to hear it for yourself.
: Meridian 808v6 & Meridian MC200 (SooLoos)
:SME 20/3 , Audio Research PH 8, Benz Ruby
: Wilson Alexandria X2 Series 2
Transparent Opus Speaker & Interconnects - Reference Powerlink MM2x Power