Thanks for your reply. In fact, you're correct -- I e-mailed Outlaw Audio about the issue and they said this:

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Thanks for contacting the Outlaws!

The Model 1050 is fully capable of driving speakers of mixed impedance. In your hook-up scenario, you will want to set the 1050 to 4 ohms.

Please do not hesitate to let me know if you have any other questions.
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Alex Bischoff