I had Richard Holder mod my DC 13.4s many years ago, and I reckon it's excellent. I've tried some of the expensive "ANR" headsets, and I like mine better.
The conversion (and most ANRs) are designed to run with 9 volts, and NiCd or NiMH batteries don't provide enough volts for the system to work properly. Buy a box of PP9s from ComDir, and keep them in your flying bag.