... what do you feel are the "most important qualities" that you are looking for in that speaker ? ...
Is the attack of percussive instruments clearly defined and musical?
Can I discriminate all the different cymbals in a drum kit easily?
Do I get a sense of swing when listening to a pianist, can I visualise their fingers manipulating the keyboard, or is it just piano shaped notes?
Can I hear the fibres in the bow scraping over cello strings, or is it just deep toned "string" sound?
Do choirs sound like a group of people singing, or just a chaos of vocal sounds?
Do kick drums snap and hit me in the gut, or just boom?
Can I hear the key noise on woodwinds when I KNOW it is there on the recording, or is it masked?
Can I easily discriminate the instruments in a string quartet - does a viola sometimes sound like a violin?
Can I easily discriminate the instruments in a saxophone quartet - does an alto sometimes sound like a tenor & vice versa?
Do oboes and clarinets sound like someone playing a wooden instrument, or do they just make "wind" sounds?
Do trumpets and trombones have that lovely rude, braying sound - or are they just "brassy"?
Does the music make me want to dance / sing / join in somehow?
Can I play them loud (ie you can't possibly talk over it) without the music seeming oppressive?
Do the treble sounds make my ears ring at high volume? (BAD!)
Do the midrange sounds seem distant? (BAD!)
Do the bass sounds seem prominent? (BAD!)
Do the speakers sound immediately "spectacular"? (VERY BAD!)
Of course, all that applies to the system as a whole, too, but it's what I listen for.
It's also essential to listen to music that you like - it doesn't have to be albums you know well, just the type of music that you will want to play. Don't be misled by advice to test by listening to violin music, or piano music, or organ, or female voice, yadda, yadda. All of that is pointless if what you WANT to listen to at home is Steve Vai and Joe Satriani.
For example, the first time I heard Lowthers I was astonished at their speed and accuracy of nuance - many of the points on my checklist were there in spades. That was listening to a jazz trio - then I listened to a solo piano and was even more stoked - then I listened to some Fila Brasilia dance/house/electronica and the whole thing fell flat on its face - the speakers just weren't made to do that sort of material. Nothing wrong with the speakers, nothing wrong with the recording - they just didn't like each other.