If you used bell wire then the sound can degrade over 15 metres of cheap stuff (over any distence of Bell wire)....get a minimum of 42 strand oxygen free copper stuff and you'll be fine....If your meaning a time lag or dealy in the signal then No....it would have to be a much bigger distance before any effect was distingushed.
Yes it would, but the difference in location in the room and the fact that they are behind you both have larger effects so don't worry about it.
sft42 is right, get cable with a decent amount of copper in it, bellwire is a poor excuse, the number of strands is a bit of a red herring though, single core sounds good, it's down to how much copper in the first instance, then start worrying about oxygen free, or long grain crytal etc