OK, I just got off the phone with Panamax and here's what they (she)had to say. The main difference between a model like the 5100 & 4300 is that the jacks labeled high current have 2 distinquishing features.

1) ability to delay on/off
2) removal of some sort of voltage coil. She indicated that in order to hear this, you would most likely have to be dealig with equipment in excess of 10k for amps. She isn't saying that some might be able to hear it, but usually so. She actually has a receiver with an outboard amp and said she noticed no difference whatsoever.

So, that clears it up a little for me, but I may still go with the 5100 for the delay feature.