The shack has various lengths of shielded cable with 90 degree molded plugs I get 2 solder-on plugs with each one and for interconnect cut to length and solder the plugs on. Where the plugs are exposed like the mixer I plug in the factory ends. In humid climates would use the gold plugs. Good shielded cable has a woven shield (maybe 2) and has a braided center conductor. The impedance isnt critical until you get up to video or rf frequencies (unless you have long runs) Then you should be using 600 or 1k ohm balanced anyway.
For speaker wire I used to use the zip cord style Just make sure the wire is of the proper guage to handle the peak currents to the speakers.
Here is a link to a tutorial on hooking up audio equipt.
www.rane.com/note110.html