The impedence ratings for my Logans are nominal 4ohm with minimal 1.2ohm. I've not had issues with overheating on my 7500.

Rob
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Yamaha CX-A5000 pre-pro
Outlaw 7500
Oppo BDP-83
Samsung 65" LED TV
Front: Martin Logan reQuests & Logos
Surround: Martin Logan Fresco i via Outlaw OAWA3
Sub: ACI Maestro w/ ICE amp