"The big problem with using very small or narrow "disappearing" speakers is that they employ small drivers => the trade off is higher distortion (particularly in the bass and lower mid), poor dynamics, and poor performance at higher (live music) volume levels. However, for nearfield listening at close range (most domestic situations) this design is clearly the most popular in the industry today."
The Dynaudio S3.4 comes to mind, as it is only 7.5 inches wide, and has two 17 cm (6.5 in) woofers...anyway this is a very remarkable, serious high end loud speaker. It can fully "dissapper" in the sense that when you look at the speakers during play, they seem like they have nothing to do with the enveloping soundfield all around you, and they can play loud as hell with very deep well defined bass. They are very thoughtfully designed/manufactured and have to be one of the best values capturing modern speaker design, available. And this at 9-10 feet from them, not what I call near field for 1st order designs.
I happen to have their little brothers, the contour 1.8 MK II's, that also image well, but do not go as deep or as unrestrained during super loud passages.
AGain, both of these are fine examples that one need not spend 25K on speakers to get the dissapearing act. Sure you can do it, but your speakers are not the only things dissapearing at that point (savings account balance anyone ;) )
Happy Holidays All