Yet another view of the "wire salad"!
Now everything is way more organized and accessible. I used huge amount (literally - pounds) of ferrite toroids and split-core ferrite beads to form common-mode current chokes on almost every cable. This resulted in a electrical noise-free environment. Most of the chokes are installed on cables connected to the PC. Right in the middle of the image is visible the copper ground bar. I used wide straps made of copper foil to ground each piece of equipment to the ground bar.