First the Room EQ is an outcome - it shouldn't be a target... (as per postings by Floyd Toole)
It will vary from room to room, as well as from speaker to speaker.... the Room imposes its response primarily in the under 500Hz range... but reflective surfaces can affect the high frequencies as well, although our ears will mostly filter things out psychoacoustically as long as the reflected sound is sufficiently delayed from the direct sound.
Hence the flaw with the use of the "Target Curve" - it includes the reflected sound which our ears filter out!
So step one - have a set of speakers you LIKE the sound of.... ie: the direct sound of the speakers is good.
Step two, apply RoomEQ to adjust response below 500Hz
Step three - use the response of the main speakers as a template to define a target curve for the other speakers (ie: voice the surrounds, heights and possibly center, to match the mains) - apply this Target curve to everything except the mains. (if the mains and center are tonally matched, don't apply to center)
In a perfect world, we would use methods such as time gating (measuring response within a limited timespan from the original signal, so as to exclude reflections) to define the target curve from the mains.
One of the potential benefits of ART, once it gets extended further up the frequency range, will be the potential for it to actively cancel some of the reflections that can muddy the sound.
Based on what it does, it may also provide us with the ability to identify/see/measure the direct sound without the reflections, and therefore define the required "direct" target curve.