Thanks for all the contributions to my OP. I think I'm going to take plunge on the TP PSU for my Node (2021). It seems to be a consensus that you would have to spend a lot more on a new streamer to see a significant SQ jump from an un-modded Node.
Additionally, considering how well thought of TP PSUs are over on the Naim forums, I don't think there is any doubt over the quality of TP products; Naim users are pretty fanatical (in a positive way) and discerning about what non-Naim gear they insert in to their systems.
Thanks for all your thoughts, much appreciated 👍