Monitors that play huge

The C1 or the S1.4 would both fit the bill. Few monitors (if any can compete). I actually think that for a big room like that the S1.4 is the better choice since it has even more bass output than the C1.

Other monitors that play big:
Joseph Audio Pulsars
Usher Be-718
Fritz Carbon 7s
Totem Mani-2
Wilson Benesch Discovery

In a second system, I have Merlin TSM-Mmi in a living room the size of yours, placed on their sides at ear-level in a huge, open-sided and open-backed, solid birch wall-unit, which is on a short wall. The room is untreated with lots of hard surfaces and big windows. In other words, it's a challenging environment for good sound. Driven by 40 watts of El84 tube power (Stingray) with a 12-in. subwoofer tucked inconspicuously in a corner, the TSM can absolutely rock the room, or I can play them softly as background music during parties. Either way, they sound very, very good--way better than I expected. No wood veneers, though. And a sub is needed in a room like yours, IMO, unless you get some pretty big monitors.

C1 sounds huger with more punch weight, more refined sound,better soundstaging and separation of intruments,but highs are a bit roll off compared to contour
But if budget is limited, s1.4 great choice as well.Has very rythmic highs.Sounds great with all type of musics, more dynamic in bass region than c1.Later on you can add subwoofer for even more bass and sound impact
I have both speakers and enjoy them .Sometimes I want trade s1.4 for subwoofer,but when i turn them on,I dismiss this idea:)
C1 require more power,opens at louder volumes while the s1.4 is not so picky abaut other components

C1 require more power,opens at louder volumes while the s1.4 is not so picky abaut other components

The C1 MKII/Signatures play great at all listening levels unlike the originals and don't seem to need as much power (rated the same). So in my opinion if you like to listen loud then the originals are fine but if you mostly listen at lower levels the MKII's are much better sounding. I have a sub with my C1 signatures but honestly it only really helps with recordings that have extremely low bass notes that the C1 can't physically reproduce.