http://www.polkaudio.com/forums/showthread.php?t=46763
Any help would be appreciated

Just to cover all the basic things first, I assume that the switches for each amp channel are set to "unbalanced" since that's the connection type that you're using.

Yes.

You say in your original post that you've replaced an old 2 ch amp. Are you just using L&R channels on the amp, or all 5?

So two amps have done the same thing, all five channels behave this way (no output whatsoever from any of them), you can move the pre-amp cable to a different amp and get sound, and you can move the speaker cable to a different amp and get sound (suggesting that there's no short at the speaker end to put the amp into protection)... Now that is weird.

Some "shot in the dark" things to test that you may not have tried yet: connect the 7500 to a different outlet and connect a different source to the 7500 (even if it's just an MP3 player).

Not to insult you, but here are a couple of obvious suggestions that I don't see mentioned...

Both the master power switch on the rear of the amp, & the one on the front are on?

If using the trigger, is there 12V there to power on the amp?

You didn't accidentally connect the amp to the Denon's multi channel inputs?

You don't by chance have the amp plugged into the receiver's convenience outlet do you? It certainly won't be able to deliver the power needed by the amp, maybe producing weird results.