I formerly agreed with Teo, but after getting a VTV amp with the Purifi module and the Sparkos op amp, I am truly impressed with the sound in my system. It sounds neither warm nor cold, but reveals an amazing amount of information in such an utterly clean fashion. Same with my impressions of my friend's NAD M33 integrated amp, which has the Purifi module as well. Both operate as cool as a cucumber. I am being made a believer, in spite of my dislike of early Bel Canto, Red Dragon, and Nuprime Class D amps... which sucked the life out of the music.
This is a quote from a well known speaker manufacturer who will remain nameless, but I trust his ears, because I am hearing the same thing he is:
"Yes, I have read and heard many good things about the Purifi amp modules. Maybe I'll try them. I have been using the Cherry amps which are very good class D also. This technology will eventually push AB amps out of the market."
Class D technology has arrived and is ready for prime time and with the Cherry, Apollon, and VTV amps, it is very affordable. If you have the enough coin of the realm, I suspect the new Merrill Class D amps would be incredible. The GaN technology is on the cusp of a new era in amplification as well.