I get great height effects from my regular 5.1 setup. When I tried PLIIz and DSX height channels, I didn't hear much of a benefit. But I guess it all depends on the setup, speakers, positioning, room acoustics etc.
Here's a cut and paste from a review I did last December:-Height Channels:-
I've been using surround back channels for the last three months but have found that they don't offer much benefit over 5.1. Probably because my room is fairly small (12ft by 22ft) and they were positioned close to the side surrounds. So I decided to re-position them as front heights instead to see if Dolby PLIIz or Audyssey DSX processing brings any benefits. The pic below shows how I positioned the height speakers. They are "Monitor Audio R225HD" which can be used horizontally as a centre speaker.
I mentioned above, the hassle of having to loop through the huge amount of sound modes with one button on the remote. I got round that problem by controlling the Onkyo via the network port. I was able to switch directly to the sound mode I wanted to try. I'll post more about this in a future update.Black Snake Moan (DD 5.1):-
I watched the scene where Samuel L. Jackson plays his electric guitar in his shack and it starts raining. In native DD 5.1 mode, so no heights, the effect of the rain hitting the roof of his shack was very realistic. It really sounded as if it was coming from above and sounded just like it does when it rains on the plastic roof of my shed. Activating the heights in PLIIz mode didn't actually improve the sound much at all. The rain and thunder effects didn't change much. There was a slight change to his singing voice, I wouldn't say it was for the better though. Again, I didn't hear any noticable improvement to the sound when using DSX heights instead of PLIIz. The sound was great to start with and DSX heights didn't change much.Blade Runner - (Dolby True HD):-
I thought this one would be good to test as it has a lot of height stuff in the sound. It practically rains all the way through the film and then you've got all the flying cars and hovering advertising things. In native Dolby True HD 5.1 mode it does sound very good and all the aerial effects come from where they should be in the sound stage. Activating the height channels doesn't really make much difference at all in either PLIIz or DSX mode.Stereo Music:-
Nothing sounds better in surround than a bit of symphonic prog
. So I put on "Collage - Heroes Cry", corny lyrics, but they are a Polish band so I guess you can forgive them that
. It sounds fabulous in Stereo with the Audyssey EQ really opening up the front sound stage compared to Direct Stereo. Switching to PLII Music mode is stunning with the symphonic keyboards soaring up all around you. Using the heights in PLIIz didn't make that much difference compared to PLII Music. I noticed that the vocals were very slightly less focused with the heights activated. With Audyssey DSX, you have to matrix the sound up to 5.1 first. You could use DTS Neo:6 Music with DSX Heights but I tried Dolby PLII Music with DSX Heights. DSX didn't sound too good. The soundstage was moved towards the front and it was a bit heavy and leaden compared to the airy hi-fi sound from PLIIz. Out of the two height processing modes, PLIIz was far superior in my room with my speakers but I still preferred the regular 5.1 PLII Music mode.
So, in my room with my fairly decent 5.1 speakers, I didn't experience a greater sense of immersion by using front height speakers so they'll probably be coming back down at some point.
I still think getting the highest quality 5.1 setup is still the best way to get superior sound quality rather than a dozen average speakers around the room.