I owned dt770 80ohm and he-400 at the same time. He-400 has less bass quantity, but better quality. They both extend really low without dips. High's are way hotter on the he-400, to the point i find them really uncomfortable. Dt990 was unbearable for me. I dont have experience with the 250ohm dt770, but supposedly 80ohm version has rolled off treble and more bass compared to 250ohm. Not sure though, based on my readings alone. I preferred dt770/80 over he-400 for sure, part of because im a basshead and they were more to my likings for gaming and random movies when im alone. Music alone, he-400 was clearly superior in almost every way, only con i could think of was hot treble, but it got better with the jergpad mod. Still had to eq a little.