Best way to wirelessly transmit audio within house

CD player downstairs. Denon receiver (using zone 3 to feed house speakers) UPSTAIRS. I cannot get a clean signal due to walls and floors. I have tried FM (CRANE) - not enough range, Motorola Bluetooth (nope) and closest of all, Audioengine W1. The signal gets there all right, but there's way too much noise hiss and hum under everything. The problem is interference, likely from something within the Home Theater equipment, i.e.: is not in the amp or the house wiring. Can you suggest something?