I tried both QS8 and M22s as height speakers and found that in my room the QS speakers worked better but I think that’s partly because my height speakers are outside of my mains not inside like yours so you might find that M2s would work ok for you.
How much height speakers will help is room dependent. If you already have a high ceiling with a lot of ambience they probably won’t add a whole lot. Actually in my room the height speakers are the least impressive of all the speaker locations including wide and rear. An I probably benefit from them more than most since I have a very big screen and my front 3 speakers are all below it. So using the height speakers can pull the ambience of the front soundstage up making a little more of a “wall-of-sound” effect.
Note that the only thing coming from the height speakers is ambient stuff like wind, rain, echoes but you could probably get close to the same effect in most room by just moving your surround speakers up higher. Because the effect only happens with ambient sounds the height channels don’t come into play as often as the other ones.
If you have a friend who can loan you a pair of small bookshelf speakers you could try them out as height speakers before placing an order. Otherwise I probably wouldn’t spend more than for a pair of M2s at the most a pair of QS4. Which should work marginally better than m2s but that’s going to depend on your room.
Because everything coming from the height speakers is ambient I don’t think you would even notice if they were laying on their sides.
As for PLIIz vs DSX height I can’t tell the difference, but then I almost exclusively use the DSX wide mode anyway. BTW what makes you think you don’t have room for wide speakers? A couple M2s on wall brackets aren’t that obtrusive (says the man with a bat cave).
Cheers,
Dean
