What makes speaker's sound big?

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.

There’s a lot of talk around the hot porridge, as they say (i.e.: to beat around the bush). That is, important parameters (not least acoustics and general implementation, that needn’t be expensive) have been covered already as a basis to achieve "big sound" in some form or another, but depending on the size of the listening space true room fill and effortless physicality will not occur without the addition of ample, effective air radiation area down into the sub octaves. Spatial size and overall coverage can be had from a fairly small speaker package - surprisingly small, even - but compared to subs augmented much bigger speakers with full range bandwidth it’s mostly just puff air; true big sound has that alluring quality of immersive presence and inherent, effortless power to it, even at lower volumes. A smaller listening space will be less demanding with regard to speaker size/displacement area, but the more authentic sense of real, sonic size and girth as anything reminiscent of a live event requires a moderate to large listening room and not sitting too close to the speakers, and this in turn will place more demand on speaker capacity and displacement area. I know, big speakers aren’t popular (typically not in the eyes of the missus), but there’s no way around blunt physics - again, all in relation to the listening space needed to be covered.