Well, that may explain why my experience was so different from yours. The bass on the Blu-ray was powerful for sure, but it wasn't overblown, gratuitous, or annoying. I'm familiar with overblown and gratuitous LFE from the HD cablecasts of the Star Wars movies. The Blu-ray of Iron Man had none of that. I've had some soundtracks make my subwoofer bottom out, but Iron Man did not.
So I guess the mixdown for std-def DVD is significantly different from the Blu-ray.
So I guess the mixdown for std-def DVD is significantly different from the Blu-ray.