How much capacitance can I add (upgrade) to the amplifier's PSU?

[Loboscope]

I am sorry, but this video is a fake and pure nonsense. Nowhere in the world exists a 128´-Organ Stop.
And there are only two organs in the world with a true 64´-Stop going down to the subcontra-C: Australia, Sydney, Town Hall and USA, Atlantic City, Convention Hall. Sometimes there do exist ´fake´ 64´-Stops, that means, that this Stop is build with a 32´ together with a 21 1/3´-Stop (Quint). This combination gives a sub-octave tone qua a difference-tone, but this virtual sub-octave sounds relatively weak.

The Organ in the video might let hear a 32´-Stop. But anyway a 32´-Stop goes down to 16 Hz which is nearly the lower audition limit of men and a 32´ open pipe Stop or 32´ tongue-pipe Stop will give a great sound impression and will demand really good audio gear. But so will do a 16´ Stop  as well - it goes down to about 32 Hz.

For further information look here (sorry, I only can find this german site): http://www.die-orgelseite.de/kurioses.htm

[Beamin]

Isn't an A/B class amp used for audio; powering speakers? Well I know it is but are there other uses?

[Simon]

AB is the usual option, you could use class A for low power but being only 50% efficient if not less is the reason AB is used. You can also these days use a class D that is basically a power PWM encoder, running at a higher PWM frequency than you can hear or than the speaker can react to you never hear the PWM and just the encoded sound with maximum amplifier efficiency as the transistors are on or off and not acting as power potential dividers like classes A and AB.