The Eminence 1040 SF is the long time heir apparent to the original drivers in the older ESS speakers with 10" drivers. If you plug their TS parameters into one of the online calculators, the cabinet volume of the Rock Monitor is correct for a pair of them. If you can lay hands on a set, it's probably a good thing to do.
Below is the schematic of the crossover for my generation of the Rock Monitors. However, yours looks a little different. I believe that there was a rendition with 4 ohm woofers at one point, so you may want to post the values of your existing capacitors to see if we can determine what the impedence of woofer your crossover was meant for.
AK ESS guru
@automojo has also pointed out that the 1040 SFs would benefit from a Zobel network, which is easy enough to calculate and implement when and if that time comes.
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