This thread seems to be about "external eq vs. proper acoustic design" and IMO, everyone's points are good and correct and valid.
However, I would take some exception to the thread's seeming "slant" towards external eq in the monitor chain being "evil".
I do totally agree (and really like the phrase) that the goal in acoustic design should be to build (or fix) rooms to be "quasi isotropic."
But it is a fact that most of the studio designers and room tuning gurus ( at least in the US) use some external eq to fine tune the room---not to correct large modal problems, but sometimes to make small corrections and/ or achieve a certain "curve", which can be VERY important to some engineers in some facets of studio monitoring.
I've spent 100's of hours listening to and working with various external eq's, in a very wide range of rooms--and some hardware does clearly sound bad. However, some products are very close to transparent, but I've never heard anything utterly invisible. As always, the use of any gear in the signal path has compromises.
Without external eq, some music production operations would be impossible. Try talking to Dolby about a film mix room that does not conform to an "X" curve....you won't get very far. I don't think any designer could build a room and install speakers that conformed to an "X" curve without any eq. Having worked on a lot of film rooms, in close cooperation with Dolby, I understand the powerful need for standardization of monitor curves.
You may say, "but we're talking about music studios, not film rooms", but I would ask what about the many "music guys" who are more and more starting to add TV and indie film mixing to their scope, in order to open up additional income streams and get hip to the changing definition of "recorded sound media." ...should these people tune their speakers to a small room "X"; or have multiple eq settings (shudder)?....these are additional thread topics, food for thought, but speak to the necessary use of external eq's.
As always, "buyer beware" and yes, some of the gizmo's being hawked out there are crap. I'd love to elaborate on that, but would get in trouble with some manufacturers. Some of the available external processors are amazingly powerful, if used judiciously. They can be very cost effective as well, compared to re-building walls in a room that has small issues; or, as an alternative to other filters and crossovers built as part of a speaker system. The use of any external eq in the monitor chain can be used wisely and with great positive effect, in different applications, but it won't replace good room design and acoustics. Brett's approach to first "deal with the room" was certainly good practice.