Ok this will be a good thread.

in this case one-D thinking cannot be precise since saying that speakers or amp are the most important components is just like measuring the length of a shadow not knowing the actual position of the subject.

less demand certainly on the speaker if the amp is hell of a beefy and strong and the other way back.

how about building an amp or an active speaker with amp that perfectly accepts a speaker's impedance curve huh?
than the system will totally relay on source and pre-amplification. what if an amp is quite sencitive, having high input impedance and your listening room is not too big?
yes, you can get along with passive preamp and now the source is the most important component!

or i can offer you a simple statement:
i have a speakers but i know that there are better; i have an amp, but i know that there are better; but i have them together and i love them ONLY together...

one and THE only one exception and probably the most important part of a good 2 channel system is the music that YOU love - that's definitely number 1.

I just want to add something to the speakers:

If you hire a professional acoustic engineer you can get away with spending a fraction of a branded high-end speaker price and you'll have a sound perfection for a PARTICULAR listening room. Certainly whenever you change your place the speakers might not sound right but I've seen that work wehre an engineer used the simpliest and cheapo pierless drivers widely used for DJ purposes to design an entertainment room that is now completely full with great sound and will certainly sound better if you change the source or amplification rather than upgrading the speakers so go and figure...

OK folks,
If you hook-up cheap headphones some Coby stuff or so with descent headphone amp let's say Grado and start swaping CD-players or analogue setups the difference will be much more audiable than if you would change speakers for a pocket CD-player.

There is a point where for a particular room there can't be better speaker and amp and anything invested onto these components will just produce no positive result.

And here we have a debate or arguments what goes first egg or chicken. Everything is variable and needs multi-variable understanding.

I would draw the following curve(s) and describe them by words:
1st point. Let's say I have $100 pocket CD-player,Nad 50W/ch receiver and starting with Boston Acoustic speakers.
2nd point. I upgrade speakers to B&W CDM1 and somewhat shure that it would be better upgrade rather than investing to a new CD-player or amp(meaning and always meaning smaller investment for a better sound)
3rd point. That's where the curve might split or at least take a different direction where non-speaker investment will be more appropriate than spending on speaker?...
4th point. ...might bring you either back to the 2nd or realy towards non-speaker upgrade i.e to the 3rd point.

The so called importance curve of the system components can be represented very similar to the output tube or transistor characteristic as a family of curves. The orts are Performance(vertical) as function of Money Spent(horizontal) with only ONE constant component which is ROOM.
The only exception i guess will be the source especially if it's analogue. While Speaker, Preamp, Amplifier will have the curves(parabolic forms) exactly as shown here similar to output characteristics of bipolar junction transistor are introduced:Page 4 Fig 3 the SOURCE will have a straight line (Performance = C*Money Spent where C is a room constant or let's say tangent of horizontal corner of the function) towards an infinity or the most expencive source component ever produced.

Please, note that there might be exeptions or different even improvised jumps of such curve family(just like in reality) and you might visualize just by only drowing the curve of your previous upgrades that while power amplifier can be considered as if it were an ideal match to the speakers. Thus there can be upto many speakers of a different price range that perfectly matched to the amplifier and will produce significantly larger improvement if the money spent for the amplifier.
On some point source reaches the speaker curve and that's where money spend onto the source will produce much higher results than on speakers or any other components.

Le'me put it straight!
IMHO the author somehow propheted that in this thread there will be two members as Marco and Mark.:-)

Whoever speaks that speaker has the most complicated load curve complexity I dare to place a microphone next to speaker.
The turntable cartridge follows right-after.
CD-players are linear and by default have realy no such complexity as cartridge, microphone or speaker.