Wow, this thread has my bent wheel spinning. VTV, Buckeye use NCORE or Purifi modules. They are essentially system integrators. Build a box, but a front end in, tube or SS, add a power supply and some connectors and you have an amp. Need a little harmonic richness in your setup? Add a tube front end designed to give you the best balance of 2nd and 3 rd order distortion. Want clean? Choose an opamp you like.
I need 12 channels of amplification for my new theater build. I might just DIY something. These modules are very well documented. I would probably go with a linear power supply because I can design those easily. SMPS are harder.