I replaced all the power cords on our downstairs system with NBS Omega 4 over time and it appears to me that there is a synergistic effect in using the same cord throughout the system. I am using the Omega, which is the Omega 4's big sibling, in our upstairs system and I find that the Omega 4 already exhibits many of the basic traits of which the Omega has in spades, at rather different price points: clarity, quietness, natural tonal balance in the midrange, extended highs.
The "downside" is that the Omega (and Omega 4) do a great disappearing act. What is left is only music.
If you check on Audiogon, you should find a good deal on the Omega 4s in the 300 USD range.