I would NOT recommend a Shiva: it is a very nice cord, but lacks "flesh on the bones." At the very least, one needs a Vishnu, but even this is not enough, I think. Having had all the Nordost cords, I opted for Shunyata power cords for the lower noise flower (Valhalla WILL have a lower noise floor than a Python Alpha: not so sure about the Phython Alpha Helix). The Shunyatas have considerably more tonal color, are dynamic and music sounds like itself, instead of a skeleton of such.
I'm sure there are other contenders, but be careful NOT to use the power cord to compensate for flaws in your system. You will never have a truly balanced system if you go that route.