Absolutely not the case - with Avantgarde speakers at least.Using all class D will give your system a single voice and much better for integration. When used with tubes for eg the integration will be odd ..
But the result is unlikely to match the best brands' Purifi amps. Where would you get the basic Purifi board from? Purifi offer cheap Eval(uation) boards that can be bought online, but the big brands that use Purifi technology build under license with improved components and performance. NAD, T+A, etcI would agree anyone with some basic knowledge could build up a Hypex Or Purifi class D amp. I don't know if VTV has their own proprietary power supply. That seems to be a big impact on the sonics. Especially the tube one.
You can buy boards from VTV.But the result is unlikely to match the best brands' Purifi amps. Where would you get the basic Purifi board from? Purifi offer cheap Eval(uation) boards that can be bought online, but the big brands that use Purifi technology build under license with improved components and performance. NAD, T+A, etc