I contacted the builder and got permission to post these, and he will send me some more in a bit as well.
10 KT88s per channel? That would do it. 500 a side is believable. Even toroidal transformers are going to be heavy.
I notice a marked lack of transformers, are they hanging off the back? edit: see that was answered while I was typing.
1650W, Is that a Hammond transformer? Are they using multiples per channel as I don't recall anything in their inventory designed for that much power. Could do it with 2 per channel on output.
you can use multiple output transformers for one side. The 1650W is a Hammond OT. Its basically an SVT OT. Also similar to the older Dynaco 120 / 240 OT.