What makes speaker's sound big?

Accurate frequency response AND coherent phase from 17hz to 30khz and listen at reference volume. 

Result: BIG SOUND. 

One does not need large speakers to achieve big sound and throw an immense, deep soundstage that goes on forever. But the room size matters, distance to the speakers, room treatments as well as the specific drivers for spl potential. That's why to get the above, larger speakers are often needed for large rooms. 

Can you ditch the DDs and get that in your room? If your room is fairly lively, undamped and you can sit close, yep. Obviously, not without subs and expensive speakers. 

Not having read every response I would say that the amplifier has a hell of a lot to do with the sound..

That's what I said - the amp. Speakers should be reasonably good, of course.

I had the double and packs with the 410 subs, two of them and it’s filled the room nicely. Then I got rid of the double impacts and got the moabs speaker and that really fill the room. It shakes the furniture it makes you feel like you’re there. I think you need lots of drivers to get that affect. You just can’t have a three-way speaker with a single subwoofer and get that same feeling as you can with the Tekton s

OP, don't forget Tekton makes a stand mount Double Impact Monitor.