I'm not sure that what is happening here is what you think is happening. All small, DSP-enabled sealed subs today come with EQ applied from the factory to give the magic low end extension that would otherwise be impossible in a small, sealed configuration. Done correctly, this does nothing to destroy or diminish transient response.
According to other experts this is the consensus both on the techtalk and DIY forums, with most not all people who have participated in this discussion. But like i said, I didn't agree with it at first either and keen to get other opinions from this forum, as I do have many questions that relate to this. After speaking with many experts there is still confusion and disagreement with transients in lower frequencies. I have even been told that group delay doesn't have much to do with the transient response which is contrary to what we are usually told.
.You also seem to imply that EQ can't be applied to sealed subs to even out room modes without somehow making it sound worse(?), which also isn't true
Definitely not implying this.
All I am implying is that when I apply parametric EQ or some other convolution my perfectly toned, low QTC, thumping, slamming, fast paced transient subs are not the same. If room modes have improved it doesn't bother me cause Im left with overhang from the bass that i never had without the EQ.