I’ve used Beyer 770 Studio headphones and they seemed loud to me, comparable to Sony MDRV6 or MDR7506. There are a few models of the 770 at different impedances, the lower ones will be louder. The Studio is 80 ohm, I think the 770i is 8 ohm?
I’ve used Sennheiser HD280 Pro too and way preferred the Beyers. I’m buying a pair for myself pretty soon.