A digital amp is a class D amp......but it has digital input and not an analog input. It changes the PCM directly to PWM in software and then drives a class D output stage. It does not use digits to drive the speaker. What comes out of it is analog. You might say a "digital amp" is a "power DAC". A digital amp is not a normal "class" of amp. It is just the name that TACT and Lyndorf and Technics use to describe their amps. Peachtree does not call it anything but an "amp".
Lyngdorf and Technics also make "digital" amps (Tact, now out of business, morphed into Lyngdorf). The Technics and Lyngdorf both have analog inputs along with digital inputs but the analog signal is changed to PCM with an ADC before going to the main chip to be changed to PWM. The Peacetree is the only "super simple" digital input class D amp made.....super simple meaning just a digital input and no volume control. The amp module inside the amp is inexpensive and you will see others using this technology......and other more high end complanies developing their own PCM to PWM conversion software and building their own digital amps. They will naturally be used in powered speakers, as well.....so you would have all the xovers, equalizaion, time alignment done inside speaker in the digital domain and then fed directly to the speaker drivers.....this will be fantastic! However, then there will be less to tweak....Hey, where is the fun in that? Just fantastic sound? boring....he he.
If you buy the Peachtree and love it.....you are no longer looking for analog interconnects, DACs, or Preamps.....you simple do not need these components......Using the money you save, you can get a serious inverter like the Giandel 5000 watter and the Puritan line filter after it and blow your mind to kingdom come.