It shouldnt be an issue with the amp not being able to properly cool itself off. The only time we have had a nine.2x become over heated was when the guy mounted it in the window on his rear deck, and lived in southern Texas. The amp sat in the direct sun, all day long, the sunlight alone could have put the amp into temperature protect. Got the amp moved and whalla

What voice coil config are the subwoofers? are they D4 wired in series parallel?

If they are wired wrong or D2 subwoofers. Then the amp is wired below recommended resistance.

Alex