Both cables coming out of speakers are fixed. They then connect to a duel plug. That is where you could extend one or the other. One is a basic RCA so you would need an RCA extension as one side would need to be female the other male. The other channel has an odd pin connector that I do not know. But extending the RCA should be easy enough. Whether or not it is the left or right side I do not know....and logistics at this time would prevent me from figuring out. I took a picture but I don't currently see where to attach
I live in a 3000 sq/ft, two story house, from my bedroom in the top back corner the whole house can hear it, they get pretty loud, however these are computer speakers, not designed to be at peak volume for a big party lasting a few hours, and 40+? I don't think they will be loud enough if you are having the kind of party I think you are.
No, it is not wireless system. However, it just has a nice, simple audio input cord that can plug into any computer quickly and makes it really easy to just plug it in to audio devices like iPods and phones as well. It's a really high quality system with CRAZY output. I highly recommend it.