I like the 4 Pi's very much. To answer your question about tonal quality being the same. The answer is no, and the explanation is.Both these speakers being a two way, are using the LF driver well into 1200hz. The 2pi speakers are using an Alpha 10 by Eminence. The 4pi speakers I have are using a 2226 by JBL. This is apples and oranges for me.
You'll like the 2pi speakers in a smaller environment or for fill in sound. If you have a larger area and want to open it up a bit. Youll be very happy with the 4 pi.
I had my 2pi's sitting on top of my 4 pi for a week now, switching back and forth and all around. At low volumes the 2 pi is more articualte and detailed. The soundstage is very nice. At higher volumes, the tweeter starts to bug me a little, and i move over to the 4pi, which will just tear the house appart given the chance.
Now that the two Pi's are sitting to the back of the living room. Taken on the stature of the surround speaker they were intended for. I find them perfect. High in efficiency. so I dont have to play with channel levels any more than a little seating position or delay worth of adjustment. They dont have killer bass, But that comes from a subwoofer and the 2pi is easily placed where You would like it, not where it Needs to be! (i have a few that fit that one)
last and most important. the imaging the 2pi has fills the back of the room nicely, and the crisp detail is what i wanted for in a movie.
When car drives down the road on a fall day. you can hear the leaves crunch under the tires as it rolls to a stop.
Wayne should be able to fill you in on some technical details of why tone would be different on a JBL. and then again. It may be very similar to a Theater or Thermionic 4Pi using a Delta driver.