I'm not sure how any speaker would be overkill in a room that big! 7m by 5.9m is pretty large. Plus, I don't think there's much relationship between how big a room is and how large the speaker is, unless you're going to the other way, in which case a speaker can be too small for the room. Just not the other way around. I base that opinion on the simple fact that my 3.5m by 3.6m room has standmounts with a 15" woofer in a cabinet that measure 550mm by 790mm by 220mm siting on stands that raise the overal height to 1.2m. Like you after I installed them for the demo, I thought 'no way will these work, just too big', but nope, they worked better, significantly better in terms of acoustic behaviour, than the speakers they replaced, which were literally half the size.
BTW I'm sure it's just a typo but the Alumine 5s and the Reference 2s are rear ported, not front ported.
I've heard the Divin Marquis in a friend's room with a huge system in front of it and they just didn't work; either it was the room (which is 13m by 5m by about 2.5m) interaction that was off, or those speakers were just not happy with the power amps (Audionet Heisenbergs). Five of us listening and all five of us agreed something was off. And yet, them being off was in a very large room.
The room will always play a part, I just don't think you can make any assumptions about size.