If the design is indeed different than past designs, then I guess I need to know WHAT that difference means.

Thing is, it's not. It's the same feature that Yamaha, Denon, whoever's been offering for the last few years or so. You just redesignate those back amps to the front speakers.

Mo ... if I went out and installed a second drive shaft from the transmission to the rear end of my Ford truck I would then be doubling the HP and torque value rating of my truck, right? 1,100 ft pounds of torque in a stock 3/4 ton pickup truck, wow.

Isn't this basically what you are saying?

You know what the caveat to this whole thing is? You can't exceed the maximum voltage of each amplifier. Since they're all connected in parallel, you can source three times the current but the rail voltage doesn't change. You'd have to find a very low impedance speaker to take advantage of the extra current. Having the current doesn't do any good if you experience voltage collapse.

The rail voltage of my Denon is about 35 volts. The A1400 on the other hand has a rail voltage of around 90V.

So why do they offer this then? Is it for low impedance speakers (like 2 Ohm) or is it so that you can double up on fronts?

Nope, it's marketing. Plain and simple.

From what I've read, the only real benefit to biamping comes with a) extremely high volumes and b) external, active crossovers, neither of which you will achieve with a receiver.

I think there is some confusion between bi-amping and bridging. Bridging does mean combining two channels on the receiver into one. Bridging is much rarer as a feature.

I don't think I've ever seen bridging on a receiver, but that would certainly double the power.

I think someone told me awhile back that there are very few amps that can bridge into 4 ohms.

Actually I had two lapses in thinking:

1. In the case of disconnecting the strap and using the rear channels for bi-amping, I neglected the fact that the two speaker halves each have a larger impedance while the available rail voltage has not increased. There may still be a marginal benefit but I doubt it's of any practical significance.

2. In the case of multi-channel connected to the fronts, the speaker impedance doesn't change but the rail voltage remains the same. More current is available but without voltage there is no "pressure" to push the current out.

However, if anyone has low impedance speakers (say a couple of Ohms), both of these ways would power them very well.

So I'm glad I drew that block diagram for myself .

Onkyo-875 has that (not the 805), but they don't support 4Ohm bridged.

All the home amps I have seen that can be bridged recommend a minimum of 8 ohms in bridged mode.