After some searching, I found the following info on the Internet:
"Adding a high-power DC power supply upgrade to the Naim Supernait 3 integrated amplifier can enhance its performance, particularly in the preamp section. Naim offers the HiCap DR and SuperCap DR as power supply upgrades. The HiCap DR costs approximately $2,990, while the SuperCap DR is priced at about $7,490.
Users have reported improvements in sound quality, including increased depth and soundstage, when using the HiCap DR with the Supernait. However, the extent of the improvement can vary, and some users suggest that the benefits might not be substantial unless paired with other Naim components.
The HiCap DR is a Naim product, and it’s recommended to consult with a Naim retailer for purchasing options. The upgrade is generally considered worthwhile for those seeking incremental improvements in their audio system".