Which is more important?

I would like to take my system to the next level. What ever that may be. It is my understanding that any component can influence the sound as much as any other. Being economicaly challenged, upgrades are few and far between. Therefore my experience with new equipment in my system is limited. Plus, being in the military my listening room is always changing. Reviews are no help as preamps, cables, IC, and everything else seem to take a back seat to amps and speakers. Without rebuilding a house that belongs to the U.S. tax payers. Louis