'You can try' by Saraya. Freaking dirty, rotten, sassy MF guitar that will test any system. Sandy Saraya's timbre pipes against the heavy demon distortion is hard for most amps to image. If an amp can handle the opening of this song without choking, then it gets my respect and I let her have more.
Typically, I don't use 'audiophile' tracks, I use challenging tracks to test gear. If they can get me past the nasty shit, then I try something like Sting's Summoner's Tales or Pink Floyd's gold DSotM.