Rather than evaluating it as a cabling problem, evaluate it as too much equipment for the task. Why do you have all this stuff?
What are all your external drives for? Why are they external? Do they all need to be connected all the time? Could they be replaced with fewer, larger drives? Could they be mounted internally? Would a new case help?
Are all those monitors actually helpful, or are they just cool? Would fewer, larger monitors be more useful? Could remote desktop be used to eliminate some of them?
What;s the second machine for? Is it doing something useful or is it a "file server" or some other excuse to keep obsolete equipment around?
Do you really need a network switch in addition to a router?
USB hubs? Plural? What for?