Yep - the 10s in the 210 will each see twice as much power vs. the 410 drivers. Using 500W as an example, each cab will receive 250W, which means 125W per 10 in the 210 cab, but only 63W per in the 410 (single drivers, such as 112 or 115, would receive the full 250W).
While this is true, it still sounds OK to put a Rumble 500 combo on top of a Rumble 410 if you want to, but I seriously doubt it would achieve a significantly higher maximum SPL than if paired with the Rumble 210 instead. Some Rumble Club members like the 112 or 115 better.
@WRM has the SPL King with the Rumble 500 head atop a pair of Rumble 410 cabinets.
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