Exactly. The big change is that HT has driven the adoption of subwoofers for the deepest bass, so everything else can be handled by a medium size speaker.
If you have M80s and a big honkin' sub (or two) you are going to have the same kind of SPLs as Voice of the Theaters plus at least an extra octave of deep bass AND scarily accurate response. The only change is that the bottom couple of octaves have been pulled out into a specialized (and still BIG) subwoofer.
The horn-loaded speakers were great for efficiency but the horns tended to emphasize some frequencies over others... I never even heard anyone succeed in EQ'ing VOT's to get the same kind of flat response as a conventional speaker.
You might want to PM Dennis (Tharkun on this board) and talk to him about loud. He runs a 7.1 system with 5 M80s and 2 EP600s and seems to be able to run at literally dangerous SPLs with totally clean sound.
I normally run at 85-90 dB when I'm playing "loud"... I know Dennis runs way over 100 dB and I imagine 110dB+ is more like it when the guests have gone home. A few people here have checked out the system and have pronounced it utterly clean at ear-bleeding levels.
M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8
| 
