604 w/1000 Hz XO is the rarest and in my limited experience the best performing mainly due to its best horn/woofer polar response matching. The downside and why the rest have 1500 Hz XOs is its too low usable power handling for post WWII apps.
With many high end 'full-range' drivers with nowhere near its performance costing >$2 k, this one's a 'steal' IMNSHO. If current GPA HF diaphragms will work, then all the better unless only spinning 78 rpm vinyl or listening to AM radio.
GM
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