Yeah that circuit is pretty basic/low budget. I found some quality brand name schematics for 150/300W models, this winter I should spend the moeny on a proper case, heatsink and mosfets, and build it. That had an MCU, but it wasn't required, it was more for control and a screen. I think it's some guy called Kerry Wong, his website/youtube videos
There's also a nice 1 on youtube where the guy design's one with ADC/DAC's, and iirc, it was good for 10mV/10mA steps, without costing a fortune either. And they should be pretty scale-able.