I think it depends on your definition of "important", and the goal you are pursuing.
If your goal is supreme and accurate musical reproduction, then I am with Linn on this when they say the source is of supreme importance. If the source is most important (because if you can't retrieve the audio, there's no need to go beyond that), then it would stand to reason that the amp is more important than speakers. Because it comes before the speakers in the chain, if the amp throws away something, the speakers aren't going to regenerate it.
If your goal is synergy and ultimate enjoyment of the music, as opposed to total fidelity, then the amp may be more important. For me, I found speakers that I feel for head over heels, and anything I did after that was for the speakers. I burned through three dozen or so amps trying to find "the one" for my speakers.
David Wilson argues that the speakers are the most important part in the playback chain. I understand why he feels this way selling speakers and all. Same with Linn b/c they were born and bred from their sales of good sources. Wilson's reasoning is that if your speakers won't play it back, then none of that other stuff matters. Same as the source argument really. But this comes from the ultimate fidelity camp.
If I was rebuilding a system from scratch, I'd buy speakers first. I guess the reason is that there's not much you're going to be able to do to change the basic character of your speaker. You can change anything else in the chain and it might make your speakers a bit different here or there, but it's not going to cause a revolutionary shift in the way you hear things from those speakers in your room.
Not only that, but each speaker has a vastly different power requirement as well, so you will need to buy an amplifier based on this. If you try and buy speakers for an amplifier you love, it may work, but the chances are slim that you will find true synergy, AND everything else you're looking for in a system.