But your power iron is only rated for 300VA, so the best you may be able to get is 120Wrms/channel assuming the overall efficiency is 80%
(PSU+class D power modules).
Where you get 94% efficiency that high for your moduls. What switching topology was used there?
Why you need so high power anyway? Certainly not for normal home use or your neighbours will surely complain you let alone your family.
If you really want it for certain PA use, then you got to replace a
higher VA power transformer with higher B+/B- voltage required by the module design. Say if you really want to get 2x200W/8R, then
you surely need a power iron rated not less than 500VA with B+/B-
to fit the modules. Otherwise, the power iron will get overloaded, causing B+/B- voltage drops & hence O/P power.
The filter caps & bridge rectifiers got to be beefed up accordingly.
c-J