Being an audiophile is tinkering with new gadgets. You add, audition, return, etc. based on what your budget (and wife) allow!
What do you feel is missing from your current setup?
I personally wouldn't mess with things like cables, iFi power supplies, etc. I'd spend money on specific components. Starting with your source is a logical first step.
Some say that the true magic in DACs doesn't happen until over $2K...
Maybe you start with the Schiit Gungnir USB2 for $850.
Perhaps then the Teddy Pardo DAC-USB for $1500.
Then the Chord ChordetteHD for $1800.
Then the NAIM V1 for $2400. (Pairs best with your NAIM amp.)
Ayre QB-9 DSD or Auralic Vega or T+A DAC8 for $3250.