The difference in ohm-ratings wouldn't affect the 950 -- only the amps would care about that. Likewise, bi-amping itself shouldn't hurt. Did you bi-amp the Veritas 2.1's? If not, one wiring item to check (which you may have already done, it sounds like) would be to make sure that you don't have one set of bi-amp amp channels connected to the surrounds rather than the ML's. Might even try the ML's without bi-amping, see if the problem persists -- could help with troubleshooting.

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