I often try Dirty Diana - Michael Jackson and some heavy Metallica to test the low and upper mid and kinda how powerful electric guitar and drum and bass etc in hard and Heavy Rock can be reproduced.
Try Eric Clapton - Unplugged Album to test the sound stage and acoustic instrument as well as details.
Try B.B King to test male vocal and how emotionally electric guitar sounds.
Try Celine Dion and Mariah Carey (their old songs) to test female vocal.
Some nu-metal, alternative and other type of modern rock. Also some R&B and Hip-Hop
All are mainstream music. Yep I listen to mainstream and I am currently into Blues so much
PS: I'm new to Head-Fi and English is not my native language so I think it's safer for me not to use "head-fi's terms of sound"