Hi, I don’t know if you’ve already had this demo but a few here have touched upon the right way to choose demo tunes: Listen to your favourite cd’s, the music you will listen to when you get it home.
Sounds obvious but what’s the point in buying a hifi system because it sounds great with, I dunno, Kraftwerk if you only listen to, say, Slipknot?!!
I have a Rega Saturn feeding a Naim Nait 5i and I think it sounds great with everything, although the speakers (Jamo Concert 8’s) make the system IMHO. Naim stuff is good but it’s not the only brand out there!
Good luck!