Other factors:
router is on the living room, it is a g model.
Audioroom is on the second floor...macmini is in the audioroom, laptop computer is done everywhere. Airport on mini is a g model.
WiFi reception is affected by walls, floors, ceilings as well as materials inside them (metal studs, piping, ductwork, etc.)
A wireless N network has a somewhat better range than a wireless G network. One option might be to consider adding another router between the source and destinations configured as a wireless bridge range extender.
You could add an Airport Express plugged directly into a strategically located outlet and configure it as a wireless bridge. Your existing router may or may not be compatible with AE in bridge mode, but if your main router is an Apple Airport Express or Airport Extreme, you are good to go.
Steve