what speakers do the best "disappearing act"??

Many quality small monitors will do that "out of box" thing, Totems come to mind. I have heard very cheap Mission 771s do it. I think beyond driver and x-over design that baffle area and cabinet design have much to do with it. But on the other hand I have heard it from much larger speakers too. Adding a sub with a steep x-over and a quiet cabinet will help with that all around sound.
Sean was also dead on when he talked about a preamp making the big change in his system. The electronics you use will define the limits your speakers will achieve, and many believe the hardest part to get right is the preamp. Maybe Sean will mention the preamp that sounds so good with his large speakers?

Apogee -- The Duetta and Diva not only disappear --- they stand the hair up on the back of your neck !

My two cents worth,I agree with the comments on the importance of room placement and for my other 2 cents,my friend owned a pair of 3.3`s and had great difficulty setting them up to a point where they sounded good.Even after numerous phone calls to NHT and tech support,never could get it right.We threw the manual out the window after the first couple days and tried getting creative but still a flop.He ended up selling them because of this.I am not slamming NHT or anything,just with my experience they seem to be not the most user friendly.

I agree with Catalogwiz - Apogees (I have Stages) do the best job of any speaker I've heard under $10k.

I have Vienna acoustics and Dynaudio,they both do the trick very well.