miKe mcKoffee wrote:To get similar results I image could HX the brew boiler with a beefier HX through the brew boiler!
No, that wouldn't work very well.
The original two-boiler design uses the steam boiler to preheat brew water before it enters the brew boiler. Preheated water entering the brew boiler doesn't disrupt the boiler's temperature stability nearly as much as ambient temperature water would.
In effect, temperature stability in the steam boiler is sacrificed (where it isn't critical) to allow better temp stability in the brew boiler (where it is critical). A "beefier" HX in the brew boiler would be disruptive temperature-wise.