I agree w/Jcpanny
It appears that you have two seperate audio systems. A 5.1 prewire in the LR, and whole house audio upstairs in the MBR.
Those grey wires down in the LR probably were to feed to whole house audio system source from the main 5.1 zone.
The speaker wires w/nothing connected probably used to connect to an amp that is now gone.
So where do those grey wires go ? The best way to trace these would be with a fox & hound wire tracer. They run about $50-$100.
Finding the other end of the wires won't necessily be a big deal, unless you want to use the sources down in the LR around the house.
Otherwise, you are looking at a house amp in the MBR with some sources plus the 5.1 in the LR.
You should figure out the MBR wires and speaker matching, and see how many wires you have to drive the number of speakers you have. You will also need to figure out the volume controls impendence matching wise. To do this, you should pop one out and look for a name/model # and jumper settings on the VC. Use the name.model to google up an manual and look up the jumper setting. You want to determine what the impedence match on the VC is set to. This info is what you need to select an amplifier for all those speakers.