I have wonderful news...
It's been a little over a week since my 500 has found it's way home. Unpacked, reconnected, and powered up! The power on noise I previously mentioned now sounds much more refined than before. It passed Greg's test, so I'm confident it's completely normal and must be the mag coil being energized.
The "new" amp sounds exquisite, much clearer and the music is more defined. My Polk 10Bs seem to love their "new" power provider, and play considerably louder than before.
I'm very happy! Thanks again Greg!