A good system should always sound good, regardless of source material, so I think the key is always test with a wide variety of musical genres and instrumentation and recordings both old and new, good, great and not so great (take your pick).
In general, a system that can deliver the goods at both extremes, with a variety of both the best modern recordings as well as older and more simplistic recordings, will do a good job with most everything else.
For testing low end extension and control, which is not often present in many recordings, I use recordings including the pipe organ, like the "Pictures at an Exhibition" recording on Dorian. THere are also many good recordings of Saint-Saƫns Organ Symphony that offer a good test of ability to deliver orchestral passages that include pipe organ.
In general, a system that can deliver the goods at both extremes, with a variety of both the best modern recordings as well as older and more simplistic recordings, will do a good job with most everything else.
For testing low end extension and control, which is not often present in many recordings, I use recordings including the pipe organ, like the "Pictures at an Exhibition" recording on Dorian. THere are also many good recordings of Saint-Saƫns Organ Symphony that offer a good test of ability to deliver orchestral passages that include pipe organ.