Which has greatest influence?

I am a hater of Pre-amps! after 20 years of playing around in this wonderful hobby I have learned that pre-amps have the highest potential of messing things up.

Let's say you find your dream source, a great amp/speaker combination and a room that cooperates, all that can go to hell fast with the wrong Preamp. They are necessary for switching among multiple sources (most systems for sure) and to "attenuate" the playback level (90% of the time) and occasionally amplify the input level (10% of the time?).

My most satisfying solution has been the use of a passive pre. I am currently using a Luminous Axiom pre which is nothing more than a potentiometer shunted to a quality resistor. No switches what so ever in the signal path. I believe they do offer models with multiple inputs if needed. Most folks shy away from passive pre-amps because they are not as straight forward to apply. I have had terrific results with many amp/speaker combinations as long as you follow these simple rules:

Keep the interconnect runs short
Use amps with the highest possible input impedance (30K or higher, 100k best)
Use amps with an input sensitivity as low as possible (say 1 Volt or less for full output).
Source with 2 volt outputs or higher (most players)

What that means is if your amp is rated to put out 100 Watts at 1 volt and you run your CD player directly (or through the passive pre) at 2 volts you have more than enough to drive the amp to more than full rated output!

What you get is the least messing up of your source signal. Having said all that, there are excellent active preamps out there that don't mess up the signal AND make the sound more dynamic with slightly more detail due to the fact that impedance matching is no longer an issue and the signal goes through an amplification stage (only to be attenuated again!). Good preamps tend to be expensive.

Pick the best source
Don't mess it up with the pre
Choose an amp with the sound signature you like and enough power for your speakers/room
POSITION your speakers for best sound, this can be a drawn out effort.

Cheers

The end of Bokfudo's post nailed it. During my long since past audio career - it constantly amazed me how often I'd sell some at least decent speakers to a guy and then find out they'd been set up in some absolutely bizarre configuration.I am also completely convinced that the classic British approach to a HiFi system is most likely to lead to a great result : Listen to and then buy the best source you can possibly afford , try and get some electronics that will work with the speakers you like - but the speakers will probably continue to sound better and better as you improve the rest of your system.
For instance - many years ago at the Polk factory I briefly heard the smallest and cheapest speaker those folks made drivin by a system that included a pair of Threshold Class A Monoblocks - I had listened to those speakers both in my store and customers homes a lot and to be honest - wasn't terribly impressed- wow - given simply outrageous stuff pushin 'em - these were wonderful speakers.

Stonedeaf, Amen to that. Good upstream equipment can make relatively inexpensive speakers sound great.

Jacknorth, Before going out and spending money on new electronics you may want to try some Elrod cables, power and/or speaker. I installed them and it was like putting in a new upgraded component.

Only as good as your weakest link, hard to answer. Lets say you had nice equipment and speaker cables were the weak link, I think the system could still sound fine, you may not even be aware the speaker cables are the weak link. And so some things are more important than others, and yet they're all important. I'm trying!

Having to choose only between amp and preamp, I would have to choose amp. I say that because amps have to interface with loudspeakers, proper synergy is of utmost importance. Amps also just seem to give the most 'flavor' to a system, think about all the different tube configurations possible.

IMO, all system components should be matched as to level of performance. A $20,000 preamp will make little or no difference in the SQ of a $5000 system.

However, the speakers need to be driven by adequate amplification. That is more important than the preamp as far a SQ goes. Once that is achieved, then attention can be given to the preamp. Unlike an amp or the speakers, the preamp will determine the type of control one has over the system. Does one need tone EQ, remote control, phono input, computer input, headphone output, etc...?

Mike