When I was having some rewiring done to my house, I took the opportunity to install 2 dedicated spurs for my hifi. These spurs also had their own dedicated breaker box (simply because there was no more room in the main box). So far, I've been rather underwhelmed by the improvements this gave to my hifi rig's SQ. I need to do another test one day to see if I can get a more conclusive result.
What I have confirmed though, is that audiophile fuses, and carefully chosen Power Conditioners, provide as much benefit to a dedicated spur as they do to a main circuit.That is, a dedicated spur is an additive contribution to all the other power tweaks, rather than an alternative. TBH, I found it easier to spot the differences between fuses than I could between dedicated v main circuits, but I wouldn't say that's conclusive without me going back to doing another test of the dedicated circuit once my system has settled down.