Converting transformer size to theoretical max sustained power output?

[3ll3d00d]

What's a reasonable/conservative estimate of the sustained power output of a class ab amp that has a 2.3kVA transformer? Google suggests basically multiply by 0.8 to convert to watts then multiply by something like 0.75 to get to theoretical peak efficiency of such an amp which brings us to around 1500W total. I have no clue if this is realistic estimate though (usual ai problems).

Fwiw The amp in question is an old school heavy thing, generally considered high quality for it's era, another such model bench tested suggest specs are realistic but I wanted to compare about the one known quantity (the transformer) I have