Speakers that disappear

Along with room acoustics and the speaker the gear used can be important.  I had Magnepan 1.7i's (they are dipoles) and they were a bit harsh and beaming initially (they come with resistors to tame the high end if needed).  I upgraded to 3.7i's and they were better/ smoother/less beamy.

I upgraded the amp's, pre-amp, streamer and added 2 subs and that helped make them open up the soundstage and added more 3D effect.  When I added noise control with high end switches with ground plane noise control and fiber and two CAD Ground Control boxes the speakers do a much better job of disappearing with most tracks.

Amazingly enough the amp used matters a lot as well. 

Agree with Maggie's 3.7i but they do need a high current amp and subs add a lot. . What sold me was listening to Back in the USSR. They do miss on the not to big mark however. 

Any QLN, Acora, Vivid, Vandy, and many planars.

Placement is key.  Not all speakers can be placed in the same position.  A KEF Reference speaker needs at least three feet from the front wall and the sidewalls, but a Wilson is totally different.  Even though it’s rear ported, Sonus Farber says that they are best at about 8” from the front wall. 
And of course, no to rooms are the same.