A new receiver might be fun but probably would not fix things. Plug headphones in & see if they sound clean. If the speaker cables are close to(12" or less, if paralell) the Romex running to your lights or if the receiver is on the same circuit as the lights either of those could be the source...
Perhaps your speaker cables are paralell to line voltage & too close, less than a foot between them. Low voltage & audio should cross line voltage at a 90 degree angle or should have at least 12" of space. The receiver may be on the same circuit as the light & picking up the noise. Try another...