The only speakers ADTG has that are significantly more dynamic than the Song towers are the very pricy 10k+ Revels. The infinities might be comparable to the song towers though.
Let's start with the orions.
They're an Open Baffle speaker, so efficiency below ~500hz is greatly compromised. There is a single 8" midwoofer running from 120hz to 1.4khz. In free air it is effectively very low Q as it is - qtc < .4 which means it is already 1db down from stated sensitivity at 120hz (the crossover frequency)
The baffle width also creates dipole rolloff of 6db/oct starting somewhere from 300hz to 500hz (i
could go and calculate it but no I won't). That means even if the volume displacement (Sd x xmax) of the driver allows for, say, 116db with 1000w input power @ its -6db cutoff point of 120hz, (not that he's feeding it that much power... i think his amp is 60wpc which limits him to 104db), your acoustic SPL will be lower due to the dipole cancellations. Let's say that starts at 400hz. That's an acoustic loss of 10+db so the max SPL near 120hz of the 8" woofer with the 60w amp is a mere 94db!
Add in 6db boost from the crossover at that frequency to the large peerless woofers, and you're still looking at a max SPL of 100db @ 120hz. In comparision, a pair of CA15RLYs (the mids used in Nuance's era of Songtowers, loaded by a transmission line down to the 40hz range, is mechanically capable of 115+db @ 120hz. Even if you factor in a thermal long term power handling of 120w (60w per driver), you're still looking at 109db output @ 1m. subtract about 4db, maybe 6 (outdoors) for the baffle step and you're still looking at 105db. I don't know how much actual BSC is on the Song towers but the point is, they're pretty capable. For short term peaks the rated power handling of two is 500w, so an amp, like an XPA-2, would drive them pretty well too.
Either way, 104db with 120w - that's 5db more output than the Orions at 120hz if the Dipole Rolloff starts at 400hz. If that rolloff starts at 500hz it'd be even worse (~~2db less output). If it starts at 300hz it'd be a bit better (~~2db better) but not enough to even the gap with the Songtowers.
The orions might take an edge lower in frequency but not if subwoofers are crossed over near 80hz like most setups.
Let's also consider how much ADTG likes his KEF 201/2s.. a single 6.5" LF driver.
There's a lot of factors that go into dynamics. Sensitivity, volume displacement, thermal power handling, use of shorting rings, suspension linearity, motor linearity, box tuning and box size (or lackthereof of a box a la Orion), the room size they will be used in, and the content that will be running through them. If dynamics aren't an issue (IE the room, content, and speakers will not be limiting factors) then the rest is just excess.
