I’m going to defer to Chedwin’s (Josh’s) advice here.
I’d like to add in my 2 cents worth, just looking at what 123Toid has designed and what is currently available here in the States.
Of the actual designs available, either for purchase or free, there are few choices to be made, mainly due to parts availability. You can go with either the Soundstage 15 or the Cinema 6 for LCR and surrounds, and for subs the ISO100 is a possibility, though that supply of drivers is low (9 available as I write). If you look back through some of the discussions, you can find some other subs available, but you’d have to check supply availability.
Other options are not currently possible because drivers are on back-order or completely unavailable.
The reason I don’t look at any of the smaller designs is they aren’t meant to fill a room of that size. You need something large enough and efficient enough to do the job well.
Enough of my thoughts. Josh, you’re up!