ok thanks a lot. And how im supposed to mount them? using wall brackets? these speakers are Quadral A5, they have something like a keyhole at the back.Way better. The sound imaging will move outward slightly (bigger soundstage overhead). It's not a big deal, IMO.
If you prefer, you could mount the front heights in a similar position to match the rear speakers (overhead soundstage larger than ear level). Either is preferable to no rear heights or enabled speakers, IMO, but YMMV.