what is more important ?

Hiya ,

Just wanted some views/opinions on what is the most important piece of equipment in the reproduction of sound/music.

I know and have heard that the dimensions of the room has the biggest impact but what about the speakers, amplification, and source... which one would give the biggest sonic differences(for better or worst) if replaced ?
If my current system needs upgrading which part of the chain should I focus on first to get the best 'bang for my bucks' ?

Cheers all

I started with speakers . Because everyone has something to hook to them. And sources can be half arsed while you get a feel for your room. Once you are convinced you are committed and can afford it . Get the best amplifier just above your budget , play with that a while and feel the G’s of having control of your speakers for the first time . then get a preamp you definitely cannot afford. And you are rockin. In that order. 
And also , do your research be in love with what you are getting before you even get it. Everybody is upgrade upgrade upgrade . Can you imagine the system youd have if you did waste money upgrading on half measures? .blah . 
Speakers do not change dramatically from day to day. If they seem to sound that different day to day, then there is something wrong with your system, that is, the components. 
Get the best sounding speakers you can afford first.
I think budget and balance is the place to start. Some time ago either Stereophile or The Absolute Sound put together hi-fi systems or groups that they recommended by price points. It was one of the better issues by the magazine, since it took in consideration “synergy” of components. One must know what can be afforded and what components compliment each other. Buying $60 Magico speakers and having $2k leftover for the rest of the rig, would result in not getting the best sound from the speakers. Conversely, spending $60k on source, amp, preamp, cabling and having $2k leftover for speakers would also not result in good sound. For many who know this....great. For those who don’t....big mistakes could potentially occur.