I don't know what a Powernode is, but KEF recommends 70 HP and 45 LP for the KC62 used with the LS50 W2. I use a pair of KC62s with a LS50 W2, and I'm always amazed at how well pipe organ pedal notes are portrayed.
This week I'll be replacing the excellent LS50 W2 with what I hope is a superb LS60.