Some more detail would be in order. Specifically what layout, what models, etc.. will help as well as what you are using to "calibrate" as you call it. Reason being a calibration leaves nothing to interpretation. Whereas I feel you are doing it by ear, and that does. Again more detail on just what you have. Also a room size include height, would be helpful.
It seems that you want to trust the room calibration results empirically. You can't always do that.
Def Techs have always been just a little heavy for bass, and the high end is not a bright and crisp as I personally like it, but everybody is different. I doubt that you have a Discrete DSP for each channel, which in reproduction is best ( but who has $300 for each channel?).
Without that kind of equipment I have found that just looking at each speakers overall frequency response will help to give you an idea of just what to attenuate. def tech will provide this information, it used to be on the site but I think you can request for it now. That will give you a good starting point.
Treble will have the most excitation in a loud speaker so any gain should be in as small increments as possible with no sharp rises in response, (meaning a smooth response curve).
If all else fails you can always have the system calibrated by an installer. If you really want accurate reproduction I am afraid it is the only way to go. Cost is not too bad usually right around $200 to cal a system (usually includes the video as well!).