How do small woofers produce large bass?

Hi All,

I am looking at loudspeakers... I currently own the Arendal 1723 THX Monitors. 2 8" woofers each. I listen to probably 80% home theater and 20% pure two-channel music of all sorts. I am contemplating upgrading the speakers, and there are a number that I am very interested in. The Arendals are killer for music and home theater. In fact crazy amazing at home theater. I have also 2 SVS SB-3000 subs. 

But as we all know, wanting to upgrade. blah blah ad nauseum.  :) 
 And most everything I’m looking at has 6.5" bass drivers, usually 2 per speaker. I am looking at the Acoustic Energy Corinium, the KEF R11 Meta, the Dali Opticon 8 MKII, and the PSB T600.

I have a fear that the bass will be plenty for two-channel music, but won’t have that bad-ass slam of the Arendal’s dual 8" drivers. So my question is sort of a scientific one or a physics one. I am baffled as to how the 6.5" drivers in all of these new speakers are going to produce home theater sized bass. I’ve watched every video, read every article about those 4 contenders (above) - and everything/everybody says essentially "no worries, the woofers are lighter and faster, and since there are two of them, they make a great deal of bass. I just think I’m not seeing the "science" or "physics" of that. Like how are these 6.5" drivers going to handle something incredibly powerful/dynamic (bomb blasts/gun shots/thunder/explosions etc etc???  I’m afraid I’ll be let down by something like the PSB T600’s or the KEF R11 Metas when head to head with the dual 8" drivers in my Arendals. I’m hoping people can assure me and/or run through the science....  thanks to all.    Oh, and yes, I do cross over to my two subs at 60Hz.