A stand alone DAC that also performs the function of a preamp is very unlikely to come even remotely close to the performance of a stand alone preamp. Companies have been founded on building great preamps and the best today are still built on two box designs and cost a fortune. So, an add on function to a DAC is unlikely to perform anywhere near the level of a purpose built preamp. Some very expensive DACs may have serious preamps in them.
Class D... for instance ADG sound great through for instance an Audio Research DAC. I had a chance to listen to one in my system. Amp technology should have no impact on your preamp... unless it has so very unusual output. I've been mixing and matching for decades and never had an issues... the better the preamp the better to output sound.