Speakers that disappear

You might want to check out this thread that Tvad started awhile back, as it is similar to your own question:

Speakers with imaging "Free of the box" Thread

As far as the best dynamic speakers I know of that disappear, first would be the Rockport Antares (one of the very best speakers ever made, IMHO - A friend owns these). The Eggleston Works Andra II also does a pretty good job of disappearing themselves, (and I own these).

I will also opine that planer type speakers, such as Quads, Apogees, etc., "generally" disappear slightly better than dynamic speakers, but only if you're in the sweet spot, which said sweet spot "generally" tends to be much smaller than dynamic speakers, IMHO. (This is one reason why I prefer dynamic speakers over planer speakers - I like to be social and listen with friends!).

My two cents worth.

"What affordable (Under 15K) speakers fit this description"

A lot, or none, depending on your competence in proper set up and choice of electronics and sources.

All it requires is a bit of knowledge, some money, and a lot of patience and flexibility (spacially and mentally).

Buying speakers which can 'disappear' is easy, but getting them to 'disappear' and produce holographic images is the real trick. See the thread re Holographic Imaging posted by Dazzdax.

Tvad is absolutely right - set them up on your front lawn for a couple of days - they are sure to disappear.

It might rain, so just leave them inside, with the doors unlocked !

Second the Gallos. Their disappearing act is downright spooky. I had a group of people in my listening room yesterday and one woman asked, "Where is the sound coming from?" despite the fact that they were in clear view right in front of her.