We use a 2 PC stream setup in an array of 3 computers. The 2 "gaming" computers are identical in specifications, while the dedicated streaming PC is slightly less powerful overall. The gaming computers are directly connected to the streaming PC, as well as any consoles.
Below are the main specs for each computer. Note that the power supply, case, monitor and other random peripheral components are not listed as they are not performance essential to the build.
Motherboard - Gigabyte GA-Z170X Ultra Gaming
Processor - Intel i7-6700K Processor
Video Card - Zotac GeForce GTX 1070 Amp Extreme
Hard Drive - Toshiba OCZ Trion 150 480GB 2.5"
Microphone - Audio-Technica ATR2100-USB
Webcam - Logitech C922x Pro