As long as the speaker can deliver maximum frequencies between the 20hz to 20khz spectrum, has a high sensitivity of 90+ and is at least 4 ohms in impedance, i would not worry if they are in ceiling speakers or car speakers.......
The Blaupunkt suggested sound very good, one can visit an audio dealer and hear them to be convinced....Atmos speakers only provide effects and from a value, performance perspective, I personally feel Car Speakers (2 way or 3 way design) will suffice rather than investing for in-ceiling speakers which are actually meant for announcements and channel music at low levels (using LMT).
Whether in-ceiling speakers or car speakers...max input rms power is between 20w - 55w RMS.....(Audyssey will take care of levels and tonal adjustments).