[HighRez]

Sounds like an annoying issue that the OP is having but I can also confirm that 3-4ohm loads should not be an issue into high volumes with these amps. My B&W 803D2 speakers dip well into the 3ohm range at certain frequencies and I have no issues driving them into the 105-110db zone for hours on end without issue. Still have plenty of volume control left on the table if I wanted to go more but I need to be somewhat kind to my neighbours; at least for now 

I should mention that I'm using two dual mono chassis's in my configuration with X4 NC400 & X4 SMPS600's. This no doubt makes a difference but my chassis's aren't exactly wide open either. The SMPS portion of the chassis has two small vents above the modules but the NC400 portion of the chassis is totally closed off with no vents.

Like others have mentioned, I would be interested in seeing what temps your amps are producing when they shut down. I use a nice laser temp gun when measuring mine which see 140 F at the SMPS module after a spirited session. The NC400 modules reach 120 F in comparison.

[titaniumheads]

Sorry guys I had stopped checking on this and had just made sure I didn't turn the volume up to high. That is until this weekend when my girlfriend was visiting and she wanted to
listen to Godspeed you black emperor at ear bleeding levels. The right NC400 shut down after a few minutes so I hooked up some Rowland 525 class D monos I had purchased recently. We listened to the same song for a few minutes and the right speaker volume started modulating volume lower then resuming and repeating. I have two twenty amp circuits for the whole system so I switched to a different circuit with the plug but it still did the same thing. I  have a pair of Pass Labs XA100 monos I was previously using, they sounded great and would not shut down but just watching the needles almost pegged I knew they were limited on power and probably clipping.