I also believe the earlier Stadiums had 100 watt amps. The Stadium III is 200 watts. See info at: http://www.rel.net/products/StadiumIII.shtml http://www.rel.net/products/discontinued_strange.shtml
More substantial cabinet (always a good thing), improved amplifier section, plus more flexible hookup arrangements, can hook up high-level input for 2-ch and line level for HT LFE simultaneously. But I agree, call ambrosia and ask.
I would talk to Ambrosia Audio in LA (Ambrosia.com). They are a long time REL dealer and very knowledgeable and helpful.
I do know they improved the circuitry for changing the frequency cut-off/cross-over. This is the same for all REL ST-IIIs. It makes the REL very easy to integrate. The settings have precise frequency steps in 2Hz increments.
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