Matt's right; any airborne signal will be mutated and most likely nearly "bassless". Even if the rear speakers aren't big enough to produce bass you will be much happier with the sound if you hardwire. Hide flat wire behind the baseboards or what about applying crown moulding and putting the wire behind it?

Even with cathedral ceilings the trusses should have some space between the drywall and the roof. If you get up in the attic I'll bet you can see your way through the trusses and just use a few lengths of PVC sprinkler pipe to pull wires. At $1.19 per 10' piece you just glue the couplings while you're up in the attic and then leave it up there for posterity. Get up there and have someone feed it up to you - it will flex enough to snake it towards the direction you want to use it.