For movies klipsch will afford you the most dynamic range headroom, and your room is huge. They sound good with music as well. When/if you decide to add more speakers, I would pair it with an RP 450c for the center, and (depending on the distance from the surrounds to the mlp) a pair of RP 160m's, or the older reference II series RB-81, which can be found cheap on eBay.
While I have not personally heard the JBLs, I would not hesitate to buy anything from Harman, they are a reputable company, and put a lot of research and testing into their designs, aiming for the flatest response and widest dispersion pattern possible. The 580 and 590 are both horn loaded, and should offer similar dynamic range headroom as the klipsch.
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