You don't need to author all your assets in 'HDR format.' All that matters is lighting; you need to be prepared to set up your dynamic lights with values greater than 1.f, to be prepared to set up your texture-based lights (emissive materials) with values greater than 1.f, and to set up your skyboxes/reflection maps with values greater than 1.f. All the rest of your stuff stays exactly the same.
So it turns out I probably don't need those light probes after all. Oh well, they'll make good test art.