Agreed....but not all reflections are "detrimental"
For instance, let's say you've got two reflections that arrive 180 degrees out of phase. If you effectively cancel one of these reflections, then you have removed the "damping" that occurs after the first half cycle, basically resulting in a longer resonance than you had before. I know this is an abstract concept, but I've certainly read about times when adding more actually worsens the issue. I don't mean to imply that this is certainly the case...just offering it up as a possibility.
With before and after measurements, we wouldn't need to conjecture about it - we could just interpret the data
Nevertheless, it wouldn't hurt to look at your current data after the treatment.
Btw, is there any chance that you might be able to change the geometry of your room? Namely splaying the side walls and perhaps flush-mounting the mains if that's feasible. Here's a link to a forum dedicated to studio acoustics:
http://www.johnlsayers.com/phpBB2/index.php