I guess you're just asking which is better for rear surrounds, the 250S or 160M. I'd say it might depend on whether you want a traditional 5.1 channel system where you elevate the side speakers and use speakers with a wide dispersion, or are you after a more modern Atmos style where you have direct firing speakers at a lower height. One will be better for ambience and the other better for more aggressive effects and music.
im starting with a 5.1 and asap i would have an ATMOS 5.1.2 is just for budget's problem ,nothing more....