Speaker Hiss/Crackle only on one receiver

Got a strange problem that I can't figure out and would love some help with!

I have a pair of Paradigm Monitor 9 v.5 that had been connected to an Onkyo TX-RZ820 in a 5.1 setup with no problems. I just moved to a new house and while I'm waiting to set up a new projector/screen, I got out my old Onkyo TX-NR727 to use in a simple stereo setup in the bedroom. As soon as I plugged everything in, there was a noticeable hiss and crackle that got louder when I increased the volume on the receiver. So I went to work with tests to see what's going on:
Tried swapping from right to left on the receiver, stayed with the speaker.
Tried swapping speaker wire in both configurations, stayed with the speaker.
Tried a different speaker with same wire and hiss went away.
Back to original speaker with banana plugs and then tried direct contact, hiss is back either way.
Hiss goes away as soon as I disconnect the speaker (of course).

So all this seems to be pointing to a speaker problem. But here's the part that I can't figure out: as soon as I hook everything back up to the TX-RZ820, there's no hiss from the "bad" speaker. Cranked the volume and don't notice anything different between the two Monitors. As soon as I connect everything back up to the TX-NR727, hiss comes right back. Both receivers are plugged into the same power strip going right to a wall outlet.

Anyone know what's going on? Thank you!

EDIT: Before anyone asks, even though it doesn't hiss on the TX-RZ820, I'm looking to figure this out because I'm hoping to upgrade my speakers in the projector setup and keep the Monitors and TX-NR727 in the bedroom.