Remember one thing....the cycling of your a/c unit will be dependent on where the t-stat is placed. Your house may get satisfied but the room in the attic will be hot as hell unles you manage to get a return duct back from the room to the vicinity of the t-stat.

I think I'd opt for the a/c unit assuming it's NOT a through-the-wall or window style unit. Your attic temps will be too hot to pass the air across the condenser coil and expect efficient operation. Make sure it's a small split system (indoor coil and outdoor coil). Mitsubishi makes a small system called "Mr. Slim" which has a remote condenser. However...a 9500btu unit is about 1k...a little pricy.

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Anything I say here is purely fictional. I do not use, or condone the use of illegal substances.