I've been adding things to my kitrack on and off for ages without any thought to the mess of wires gathering behind, but things came to a head when I bought a new set of surround speakers and had to take everything out and start again.
I went to Screwfix and bought a load of cable ties, and sent away for an ethernet switch and some short ethernet cables, then rewired everything keeping it all neat (I decided to go for a wired connection to my networked equipment because of stability issues on my WiFi).
I guess this isn't really a "Top Tip", but it sure made me feel better knowing there wasn't a load of spaghetti behind my stuff. My wife approves, too!!
One thing I did find is that moving my speaker cables away from the power ones as you have recommended in the past did make a difference to the sound. I don't know if this is just wishful thinking from me or if something really is happening, though.. any thoughts?