The 604E has a 1500 Hz XO, so no without significantly increasing the size of the HF waveguide [WG] and even then not a good plan going below ~900-1000 Hz where it would best blend to the woofer.
The 825/828 only loads over a narrow BW centered at ~175 Hz: http://2.bp.blogspot.com/-FhqQirgvf-...7-response.png
GM
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