I doubt power ratings for any switching amp is "sustained", but not sure exactly how to quantify it. Al could probably do it better or maybe agoner Kijanki if he is out there (both excellent EEs).
I have heard mixed reviews with Class D amps on very difficult load speakers like the Infinity's seem to be. The devil would be in the details I suppose. My OHMs are not easy, but I suspect not as difficult either. I might go out on a limb though and say that if the Carver amps can handle it, a good Class D design with a good power supply design (not stock Icepower for example) probably would do fairly well. Again, devil in the details.
I had a 360 w/ch Carver m4.0t amp for years before recent upgrades, two amps ago, running older, larger Maggies and my OHMs. Bass WAS wall shaking prodigious on the OHMs with proper recordings, well recorded organ music, etc. Bass with my Bel Canto Ref1000m is equally impressive, but night and day, way more clean, powerful, and nuanced, though I seldom get the wall shaking effects that the old Carver gear (amp and pre-amp) used to provide. I think it has more to do with the low end rolloff of my ARC sp16 tube pre-amp compared to the old Carver pre-amp than with the amps though.