5 PCs? Wow! Have you considered migrating these to Raspberry Pis? You could run all 5 Raspberry Pis for less than it costs to keep one PC on 24/7.
In fact, I'm streaming two separate feeds from a single Raspberry Pi, using two USB sound cards. Based on the CPU load I see, I bet with a USB hub a person could probably stream 5 or more feeds from a single Raspberry Pi.