There are some good tracks here.
My favourite for sorting out a big system is The Comedown from Bring Me The Horizon’s Suicide Season album: nice sub-bass synth notes under the general mathrock drum/riffage chaos and too much sonic layering for most systems to sort out at realistic/satisfying SPL. Also, sudden silences mid-track.
For a not-quite-so-big system I often go with Figure 8 from FKA twigs M3LL55X which has similar sub-bass range and sonic complexity but not the same extreme SPL requirement to really work.
Logically we want a natural/acoustic track to see how the micro-dynamics and instrumental/vocal timbres play out. I don’t really listen to that kind of thing much so lack expertise to make a good selection. But I sometimes go with The Dandy Warhols Welcome to the Monkey House (any track really) for a more laid-back feeling.
@emrofsemanon is on to something with the LEDR test though. Especially if ’test a change’ is the key criteria.
Oh, people suggesting entire symphonies are cheating. Their punishment is listening to them of course, so that’s ok with me. If we are going for length because of the ’rest of your life’ criteria, then yeule’s 4:44 (named for the track duration in hours:minutes) or one of Autechre’s n-hour extravaganzas. But neither are really good as test tracks.