I'm not real clear about the comments from the Klipsch forum. Just because your surrounds are only 90dB efficient (which is fairly respectable until you compare it to the 96dB efficiency of your mains) doesn't mean you're detracting at all from the mains - the 7100's giving them 100W each, which is a lot for a 96dB speaker. I would expect to see the surrounds needing a higher setting during calibration (or the others needing something a fair bit lower) due to the efficiency difference, but once they're calibrated it shouldn't make any difference.

Two questions do come to mind. First, have you tried higher crossover points all around (perhaps 80Hz for the mains and 100Hz for the center and surrounds)? Second, where is the sub crossover set? If it is set at the sub's amp, try disabling that crossover entirely (since the 950's already doing bass management) - you may be throwing away everything above 65Hz that's being sent to the sub (including some of the LFE channel and a piece of the data coming from center and surrounds). That sub crossover setting alone could be weakening your low frequency "oomph."