That depends on how much power you require. If you are a bass freak, always (or mostly) listen to high volume (also based on your room size), then it would be better to get an amp (stereo) match with the right speakers and you are ready to go.
Since you have D1, it would be useful to take a demo with A5+ and see if you like it. Else move to the other chain (amp+speakers+your D1).