I agree with mijostyn that the radiation pattern control of a good (low-coloration) horn would facilitate getting good spatial qualities with the speakers up against the wall. Early reflections are arguably the ones most detrimental to spatial qualities, as they have the strongest "playback room signature" cues. Good radiation pattern control in the region where we get most of our localization cues (north of 1 kHz or so) would make sense to me for your situation.
Adequate bass energy to fill such a large room calls for a "brute force approach" to a certain extent, in my opinion. Your room is ballpark five times the volume of a ’typical" room, assuming your ceiling height is the normal eight feet. I don’t know whether your big REL will keep up with your next pair of speakers or not, but two big RELs should.
On the other hand, up-against-the-wall placement offers an opportunity to get away with less air-moving capability in your main speakers than if they were placed well out into the room, but imo the design should be "voiced" with the expectation of what close proximity to the "front" wall will do to the frequency response. Not all speakers work well in the bass region when right smack up against the wall like that.
In addition to mijostyn’s suggestions, you might consider the JBL 4367 (with subs) or the JBL M2 (subs arguably optional). A few years ago a customer asked me for guidance on speakers which would work well up against the wall in a similar-sized room, and he ended up choosing to go with something custom which took into account the factors I mentioned above.
Duke
dealer/manufacturer