The 813 has a lot of unknown territory to cover I suspect. That and not-so-simple power supplies. So, it depends on where you want to draw the line at 'too complex' or too expensive' or 'too heavy' or...The topology I laid out for Merlin is quite adaptable. Remarkably so I think. Where ever you feel like jumping in, there will be support and help, and you'll probably wind up learning something important that neither of us knows now at the begining.
There are many choices, and options in this world of DIY amps, I am not used to applying blinders or shades to the development or discussion. I'm also not quite comfortable saying that there is only one 'Best' for All. This leads to a muddle of options. gather some of them up and present them for discussion, and we can try to figure out what is the better path to experiiment on.
regards,
Douglas