Oh 400 V R2R??? Man, this is for PA application not home. More details? Looks cool your pic.Sub class d amplifier 200 0 200 DC supply rails
I build it, no regrets and never found better (I've a pretty nice collection of Bip/MOS amps too so can compare).
To be concrete you can check out this link where I posted some pics and also videos with how it sounds.
https://drive.google.com/drive/folders/1WaC_oNdXpL2d_nxn6at1nQf82Wne29xB
Feedbacks welcome. Most difficult part is not the amp itself (from Elektor) but all the stuff going around, can give you quite some infos I learned really a lot with that project. Be my guest