The amp is 2 ohm stable per channel. However when bridged it is only 4 ohm stable per "bridge". If you use option 1 you would be placing a 2 ohm load across channel 1 and 2, which would not be stable . I think your best option is using option 2 because you will have a 4 ohm load bridged over 2 channels (4 ohm stable). Each of your speakers is 4 ohm which would produce the 180w x2 @ 4ohm rating.
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