Couple of questions to better understand your needs
I presume these room dimmentions are in feet? (Altough Toid(Nick) is in the USA there is a decent international membership who use metric so its usually best to specify units every time)
Is this the amplifier your using? https://www.summithifi.com/products/ad-7300pa-amplifier
If it is it can only do the 300@8ohm single channel driven. All seven channels together drops that to 180@8ohm