Two tracks? The first is easy; the other is a toss up:
1) Jimi Hendrix - Machine Gun (live from Band of Gypsies)
2) Either Tedeschi Trucks Band - Made Up Mind or a relative unknown, Kadavar's song Last Living Dinosaur. All the instruments come in separately and sound simultaneously clean and fuzzy. It's a good system test because I know very very well exactly how it SHOULD sound. Great question, btw.