IB2's with MB2 center? That is a pretty massive center channel... I would say EB's with a IB center would be more practical based on cabinet size alone. But practicality can easily be thrown out the window when talking about surround playback at the level of MB2i's

That said, sensitivity is relatively close between the two. 89db for IB, and 91db for MB.... So it's not a major disparity between the two. My question would then be: Are you going to be powering these with three Mono amps?.... Or a stereo amp between the L&R and a mono for your center? The power handling on the MB2i is significantly higher... And big PMC's love big powerful amplifiers. So that would be something to take into account.... With an IB2 LCR you could achieve very nice results with a three channel Bryston 9BSST2, or what have you. This would work with an EB1 & IB2-C as well. With IB2 & MB2-C your going to have to think about the level at which you want to rock.

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PMC, Bryston, Purist Audio Design.