Great list.

I have so many test tracks to use that it would take up pages on this form to list them all, however because you've asked for five I'll submit three red book CDs that I highly recommend to everyone to check out as far as demo tracks. They're listed in no particular order. You can thank me later.

Weather report ...sportin Life.. entire CD

Denon audio technical CD tracks 3 through 11 (to be clear this is CD c39-7147)

Al Dimeola - elegant gypsy... entire CD

Edit: of course I could recommend the highest PCM resolution that there is which is 24 /192. In that case , you want to listen to anything from the Grateful dead's St Louis box set ( in WAV format of course). That is the best digital I've ever heard... Not just because I'm a grateful deadhead but because the recording is so amazing you can hear the musicians breathing if you listen hard enough and have a resolving system.