I've used Rocket 33s for years - last year I decided to re-evaluate and tested against Blue Jean Cables and Kimber Kable (note could have just as easily been Transparent or other Audioquest but I didn't expect a big difference so I kept my comparison number small)
Well unfortunately there was a difference - I preferred the Blue Jean Kable to the Rocket 33 consistently but I noticed the Kimber Kable 12 TCs to be bright and harsh at times and other times have wonder sound stage and details during both very quiet sections and during very dynamic sections. So I tried the Kimber Kable BiFocal XLs - they made a big difference for me.
I personally would have been very happy if they didn't make a difference so I could have saved the money...but I heard it and did several blind tests with a friend on speaker cables, interconnects and power cables. And the difference was observable by both of us every time.