If the powered subs are connected to the 950's LFE output, I'd set the speakers to small and the sub to on -- that way the subs will get the LFE track and the low frequency material from the speakers. Before you add a dedicated sub, you might experiment with that. You will need to play with the crossovers a bit to find a good spot, as I don't know what the frequency response is for the 2300's.

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review