It clearly depends on what music you listen to the most, and what you want from your system. I am a lover of jazz and chamber music. I've recorded and attended concerts and know what full orchestra dynamics are, and I' recorded and listened to pipe organs. So here is my take on these.....which ranking or preference you have is up to you.
1. Vocals .... Sinatra and Bonnie Riatt are my favorates. The voices should sound like voices.... no sibilants, mistracking or any obvious reproduction issues. The vocals should have "presence" but the tonal balance has to be highly agreeable to you. Otherwise very good systems can add a little tenor emphasis or a little alto emphasis to both their (and many other voices). But in either case the voices must sound natural.
2. Jazz .... well recorded club music. Make sure their is both width and depth to the sound. As somebody stated earlier, make sure the piano sounds "all of a piece" top-to-bottom. Likewise the string bass....plucked strings should sound "all of a piece" dispite the disparate range. Brass should have no tracking issues. There is no substitute for attending a fair number of jazz sessions in different club environments to train your ears to these sounds. You might need to use several disks as references, since club recordings are difficult to record really well.
3. Chamber music ... evaluate much like jazz, live recordings if possible. Sit a few times in the closest row; a few times further back with some hall sound. Get familiar with both. Chamber music can be recorded many ways....some natural and some simply mono-mic'd.
4. Symphonic Orchestra ... make sure that you are using recordints that actuall allow the hall acoustics to be heard. Know the type of gear used (older classical music from the 50's, 60's, early '70's often showed photos/described the recording set up. Know what an ORTF mike setup sounds like; know what a three channel mono setup sounds like. Make sure your amp/speaker combination can handle the loudest sections without cartridge breakup or speaker breakup at the loudest levels you will listen.
5. Pipe Organ - Get a recording or two from a church or cathederal playing music that has 32hz pedal notes....these should be solid and if you are on a wooden floor, should usually create a vibration as well (below 32hz you will mostly "feel" vibration).
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Hope this provides help in one way or the other for some folks here.