Mike,
On your question whether to switch to Shunyata over NBS, my advise goes as follows. First off, I will let you know upfront that I have not auditioned the Shunyata line so I can not tell you whose products are better. However I do believe you may not have chosen the correct model for the level of performance you are seeking. As stated on NBS webpage choosing the right model is a crucial to reaching that the ultimate performance level from your system. And here is what I experienced with NBS cables. The NBS Monitor IV is a better cable then your stock cable, although I have found that the Monitor IV is vague on mid-high frequency detail, the bass is not as tight compared to the higher models in the Monitor line. But NBS cables are known for their ability to release the harmonic textures within the music. This is what I experienced when I first switched over to NBS. But you know all of this since you have switched over all interconnects and power cables. My advice for your system is to start looking at the Monitor II level power cable or the Omega III. Both cables are on the warm and organic side of neutral, however they are open, with lots of air, and you will get that added dynamics and sparkle you seek. Oh, last thing experiment with placement, I found that you have to listen to each arrangement of cables before you can get the most from your system. For example I use a combination of power cables in my system and I found that the highest quality AC cable should be placed at the beginning of your system (i.e. source components CD player or turntable) and go from there.
My system:
Brinkmann Pre & Amp
Brinkmann Amati Speakers
Oracle turntable
Theta Transport/DAC
Cables: NBS Omega III & IV / Monitor II and Heavens Gate Ultra Silence/ Silver Signature power cables.
Interconnects Xtreme X5s
Best Regards
Aaron