How to stream music to a PC?
Install iTunes on both computers
Sign in to Home Sharing on both using the same AppleID (it doesn't have to be the same AppleID as you use for store purchases)
Leave iTunes running on both.
Follow the help on the PC to select the Mac's music library and stream away.


Since you have added a lot of extra requirements to your question, I would just set up a Home Stereo system and have the playing computer use bluetooth or a cable connection to input sound to the amplifier/receiver. I use a belkin unit, but there are many at inexpensive prices and then you can use an iOS device to remote control the selected iTunes instance.


http://www.amazon.com/dp/B00B9NATUI/ - XtremeMac Bluetooth Connect Audio Receiver