I have two viewpoints.
The first is that they are both required, can't use one without the other, so fuggedaboutit, buy them both and crack a cold one. They are equally important to the end result of hearing music. Buy the best of each that you can afford.
The second viewpoint is the question of quality, and the question of the sequential order of choosing parts of a system. OK so I have three viewpoints.
The second is about quality, which is I think what you're getting at Charles. I think the source is the most important because the source creates the life and the magic that every other component serves. The source is the center of the galaxy, the singularity, the throne of the infinite. The source is the thing that creates the signal, so it is most important. You need a good source to make the music satisfying and meaningful. Source makes the music sound alive. It is the spark of life and the fire. It makes listening fun and desirable. It's a hobby, so source is king.
When building a system, a different importance is placed on each component than in a finished system where you are judging importance only on face-value performance. To minimize overall distortion, it is important to choose components in this order: room, speakers, amp, preamp, sources. It is the reverse order of the magnitude of the distortion contribution. Cables, power conditioning, acoustic treatments, and your ebony footer cones and green markers fit in there somewhere too, but lower, because their benefit is more subtle in distortion terms. From this perspective, speakers are the most important part of the system proper (which excludes the room,) or maybe acoustic treatment.
OK I have 4 viewpoints. I've said this one many times before, but I will repeat it just to annoy as many people as possible. When we all were young and naive and first falling in love with music and life we didn't care about the sound equipment. We fell in love with music because of the notes, lyrics, beat, and whatever girl happens to be of interest at the moment. I think we come to hifi trying to rediscover those feelings we had about music in early teens. I fell in love with music with a Sharp all-in-one radio/record changer/8 track, with dynamic cartridge and single paper driver speakers connected by RCA jack with 6 feet of 22 gage zip wire. By the time I had decent gear a few years later I was already fully committed to the listening lifestyle. So from that perspective, none of it matters as long as the notes and lyrics and beat make it to my ears. I can imagine what's missing, and I can find context and relevance of the music within the now moment of real life. That is something kids can do, but adults have lost the ability to live in the now and relate everything to themselves living in the moment. Music sounds sweeter in the eternal now, so sweet that the gear doesn't matter. Adults think the gear and SQ is important, as a separate but related hobby to music listening and the hifi industry is born.
The media disc is a part of the physical system, is it not more important than the rest? What makes the disc so valuable? The non-physical artistic creation it holds. We do consider the quality of the pressing, or the tone of the mastering job, so media is an important part of the hifi equation, one step closer to the ultimate source of music appearing inside the musicians head.
My 5th viewpoint is that of a DIY speaker builder, speakers are the most important part of the system. Without speakers to build what would I do all day? Build amps? Forget that!