tedsmithChief digital dude
There’s the tautological response - since power cords make a difference, power supplies will as well. I already mentioned some ways to improve the supply that’s there. Yes, a competent engineer could probably splice in better supplies more easily than he could design other more intrusive mods.
Everything can make a difference but whether you get more bang for the buck working on the inside of a component compared to working elsewhere in your system is quite system dependent. “Simpler” things like room treatment, dressing of cables, speaker positioning, etc. may make more of a difference (or not.)