I know that what I'm about to relate goes against recommendation but I've connected an IdPi (RPi 3B) with HiFIBerry DAC+ Pro to a
Toshiba Canvio Basics 1TB HDD and fed it with power from a Logitech UE Boom PSU:
Color: Yellow
Model: AD895M20
Input: AC 100-240V 50/60Hz 0.3A
Output: DC 5.1V 2.0A
For a case of my personal mileage has indeed varied, the above configuration works. The spinning HDD must be sufficiently low powered so it can be carried by the Pi (I specifically got it because it was cheap and didn't include added software / firmware extras - like security - that I wouldn't use).
I was resigned to the possibility of including a powered USB hub but in my case, I was able to squeak by. All I can say, is that the OEM Logitech PSU must have a healthy swag of current margin because it must be delivering more than a bare 2A. I haven't connected it up to a multimeter to check - no need because the proof is in the pudding.
Again, as they say in the forum classics, YMMV..