Sorry maguiar, I haven't looked at this thread in a while.
That's a really tough question and I'm not sure there's any consensus on an answer. In my experience I would say it depends on weather we're talking about 2-CH or HT.
For 2 Channel I think they are equally important because the system is only as good as the weakest link. The source -> preamp -> amp -> speaker connection is all important to get right. For me what makes 2 channel great is how believable it can be relative to a live performance. For example, does a piano sound like a live piano, do the notes have the same musicality and tone? Can you connect with the performer's intent because your system isn't just playing the right note, but it's also conveying how forcefully or softly the performer is playing the keys. I've often found that simpler is better here, so two good speakers with amps that work well with them fed by a good source.
For HT I think the processor/preamp is critical. The reason is the goals here are different. When two cars crash into each other on the screen, you want the audio to match that in size, scale, dynamics and importantly location within the room. It's not so important the tonality or musicality of the crashing sounds etc. because if the image you're seeing and sounds you're hearing sync up then you're transported there. Here the amp and speakers are not that critical and often people use different amps, speakers and even speaker locations. What makes all this work correctly is the processor and equally importantly the room correction. A good processor can adjust frequency imperfections in speaker/amp/room interactions, or adjust delay times for speakers that are further way, or adjust crossovers so subs can help smaller speakers, and some even adjust impulse response. This is all within reason of course which is why many people say to get the same speakers and amps for all the channels and put them in a well treated room. However, a good processor can fix a lot of stuff. The only downside to spending a lot on a processor is that unlike amps they lose value quickly because there's always something new coming out.
Anyway, this is a very controversial topic and my views are based on what I've learned in this hobby so far. I hope others will share their experiences especially if they're different.
