I have a slightly different take on this. The acoustics of the room and the speakers are part of a coupled system. It is important that they work well together. Therefore, they are both equally important.
Amplifiers must match the speakers well and be able to deliver clean power on demand.
The differences in between digital sources are minimal.
Let's not forget about the most crucial element - the recording.
So my ranking is as thus (excluding the recording):
35% Room acoustics / Speaker placement
35% Speakers
20% Amplification
10% Source (assuming digital)