Thanks for the added info RAF...

As for why they don't "feed the same cap bank" I believe the Outlaw amps are designed with self contained amp modules. This means each one takes in AC from its own transformer winding, rectifies it to DC and uses it's own filter capacitors.

The 750 used a single transformer with 5 sets of outputs to feed each channel. There are some distinct advantages to this approach--the most significant being less cross talk and interaction between channels. Even better is using a dedicated transformer for each channel so they don't share a common primary winding.

You could wire the two transformers in the 755 in parallel and and let them feed a common DC supply shared by all the amp channels. The advantage here is that if only a few channels are working hard they have huge surplus current reserves to draw on. So the "one channel driven" power figures go up substantially as usually does the dynamic headroom. Carver and others have called this "power steering" but there's no active circuitry doing any steering in most such designs. The downside is you get more interaction between the channels and generally the amp won't sound as good.

In 98% of audio power amps (including the Outlaws), the main power supplies are NOT regulated. A 200 w/ch amp might have plus and minus 70 volt DC supply rails at idle. If you drive the amp to it's rated output, they will typically drop down below 60 volts. When playing loud music that means you can have 20 volts (peak) of "signal" riding on the DC power supply rails. Good amplifer designs tend to reject such power supply modulation, but only to a point.

So if you have multiple channels sharing a common supply, one channel will suffer from what the other is doing. This is another key reason why discrete power amps (which often have isolated power supply schemes) sound better than receivers (which usually don't).