What is they best album out there for showing off the sound quality of your system.

There are some great soundtracks with superb sound:

American Hustle
Interstellar

As well as many others

Dead Can Dance Into The Labyrinth (new pressings). I think my system sounds pretty good (for mid-fi at best) given its a mish mash of stuff waiting to be replaced (total cost $3300) but this record just........holy crap!

@soundermn : If you like the SQ of Dire Straits stuff (and I do too), check out some of Knopfler's solo work. He has done a lot. I don't particularly care for a lot of it, but Tracker is exceptional. One of my favorite albums. Get Lucky is good and the first CD of Privateering is also good. 

Tracker would be my second choice for showing off my system after Steely Dan's Two Against Nature. I like the music on Tracker better but Two Against Nature may be the best produced album I've ever heard. Even better than Aja and Gaucho.

Almost any direct to disc record

"Wandering" by Yosi Horikawa. I heard it at AXPONA 2019 in one of the Wilson Audio rooms. The first track "Bubbles" is 3D ear candy. This EP doesn't touch all the audiophile performance bases, but it sure is fun. If you like percussion and sound effects, this is the ticket.