I think the price range of the components in the system really dictates what's most important (for that system). If I had $50 speakers, I wouldn't be out shopping for room treatments. Assuming you had "good" electronics, upgrading those $50 speakers to some $1000 speakers would likely give a significant improvement. Then, maybe upgrading that $500 CD player to a $1500 player would offer the most improvement. As has been mentioned, I think it is most certainly the balance that matters most.
SPeakers 90% of your sound
After "experimenting" with various cables,interconnects,conditioners,power cords, tube amps, and digital sources...I have come to this conclusion...the sound from my speakers was not drastically altered and at best marginally improved...with this in mind...I am glad I allocated the majority of my funds towards speakers and speaker stands...I have not thrown in a TT to the mix...which is my last and latest project...I am sure there are those who will disagree...but this is my findings at this time...any thoughts? That last 10% improvement will cost me what my entire system costs already....