Hi, have been away for a while but just poped in for a look.
In my experience ensuring that the power supply is as clean as pratically possible is the most cost effective improvement to make all your music and AV system perform at its best that can be done.
The solid copper wire 'True Earth' quickly oxidizes with age, so impedence is increased.
Also the ring main acts as an conductor which puts noise on ALL 3 lines. Besides the music you are also listening to the effects of this through your system. (Noise floor, detereation in channel seperation, loss of detail and timing.)
When I had an electrician put in a dedicated 40A wired spur along with a new consumer unit I also had him clean the Earth wire from the meter. (also I used my deoxIT Kit on ALL terminals) The improvements were impressive, even more so after I went on to fit a Tacima block feeding 2 BT MTU's. This led to a complete absence of hiss, hum, the noise floor disapeared.
My music was a joy to listen to again, even the TV!
Here are a few pointers. I think it is always best to start at the beginning of the chain and work down the line. Check the quality of the Earth bonding to the home, ensure it is well connected and clean. If your consumer unit is old get a new one fitted with more outputs so you can lift and seperate better the ring circuits. Put the Hi Fi onto the 1st feed using 40A wire, nearest the isolation switch (if you are not using a seperate unit) then the highest current demand rings in assending order.
Personally I use the True Earth direct feed, I think a Balanced mains or BT MTU remove all the noise anyway. (well they do to my ears!) Improving your mains supply is a no brainer, your equipment runs smoother, sounds better, last longer.
I will get my coat now before the fighting starts.....