The most important word of advise?

Room treatment, room treatment, room treatment.

find someone you trust then just listen

I must agree with Stehno. 2 things brought my system to a level that I only read about before. I added the right power device (a regenerator) for my sources, and, I added the right (or at least closer to right) power cords. I have found that the quality or lack of quality of AC delivery to your sources and electronics is the key to feeding a higher quality signal to your speakers. Once a higher quality audio signal is sent to the speakers, and the speakers are good, then you have a more pure and beautiful sound. This is when you get the focus and individual placement of instruments in the soundstage, disappearance of the speakers, a widening and deepening of the soundstage that wraps around the speakers, greater imaging and separation, and the band playing in your room. These are concepts that I heard of for years but never experienced in my room until I experimented with plenty of power cords, and a regenerator. (already had quality ic's and sc's) If you can't do dedicated lines to help clean the ac, which was impractical for me, then a regenerator was the next best thing. And, do your due diligence with power cord auditioning until your system produces that magical illusion. There are other important issues to address. Amp-speaker matching and synergy are just as crucial.

Ears rule. Don't believe what the others, dealer, wife, etc. tell you. It is your ears that must be happy. As others are saying, start with the speakers and flow everything else from there. Room treatment's are a must.

When listening to music- your favorites- try to spend an hour at least, at levels you enjoy, maybe a bit louder. If after an hour or 2
1. you want more and you are reluctant to end- good sign.
2. relieved to turn things off and leave the room- bad sign.

#1. For me usually involves tubes, either in the amps or preamp. Tubes seem to allow for longer, more enjoyable listening sessions.

#2 SS amps tend to be fatuiging after long sessions, especially at higher volumes. SS also seems flat and uninvlolving.

My advice (see Kurt:).

Unlike other advice offered, I think amps and pre are first. In my experience, I find that most speakers I put in my system sound very good, from monitors to floorstanders and I could live with many which have passed through my room. But, I would be extremely reluctant to let go of my amps and pre now that I have a wonderful match and I have heard beautiful MUSIC from many different speakers. Then it's just a matter of tuned bass and room acoustics (yes, I know, the right speakers! But, many speakers are acceptable).
As a matter of fact, I regret having sold a pair or 2.
But that's how this hobby is, you live and learn.

My advice- listen for an extended period of time- if your head hurts and your ears need a break- BAD!
If just want to keep groovin' on the music for hours and hours, turning it up- GOOD!