Well that tells us that Dirac reduce the dynamic range, but not that i need more power to reach the same level in real life. Yes if you increase the level of the frequency range that was making your amp near clipping, you effectively will need to dial down everything but we don't know that, it will depend on content, but there is also a chance that Dirac will be able to push even more level before clipping. And it's as likely has the other scenario. if we are not limited by the effective gain applied. I am no expert on Dirac, but more often than not, if I apply a wide band EQ, I'll cut some stuff and boost some, but overall, I'll be able often to bring the level in the room likely even higher. The 0DBFS reference don't mean anything anymore once you are at the power amp stage. No?Imagine Dirac increases some part of the frequency range by 5dB digitally. You now need -5dB of digital preamplification as well, to avoid signals potentially going over 0dBFS and clipping. If you then want the speaker to play at the same level as before, the amplifier now has to make up for the "lost" 5dB in the digital domain.
Simple, and rather intuitive.