I will have to disagree Nyal . If you start with the wrong speaker you can do all you want and you still have a broken experience. Of course in low frequencies the room is control and something must be done to restore smooth response. Above there though, speaker design and performance is very important as it dominates the sound we hear. I have taken good speakers and put them in horrible places and you still get a nice experience. The reverse is not so true.I guess it depends on the context of the rest of your system. Rooms are IMO the largest influencers of what you hear after speakers. So it would be speakers --> room --> everything else a lowly third.
This is a nice graph that I borrowed from Alan Devantier (of Infinity/Harman fame):
I think the right answer is that sometimes one matters more than the other. So you would want to do both. Trying to assign priorities just gets one in trouble .