Can I run one channel of my Crown amplifier at a different impedance than the other channel?

Yes. All dual channel Crown amplifiers can be treated as if they are two separate "mono" amplifiers (One channel completely independent of the other) For example: A Macro-Tech 1202 can function with a single eight-ohm speaker on channel one and four eight-ohm speakers (a two-ohm load) on channel two. A Com-Tech 410 can function with one or two eight-ohm speakers on one channel and the other channel switched to 70-volt operation.