I currently own a pair of Ultrasone HFI-580 that I use with a Fiio E10. I know these don't need that much power to be amp'd effectively. My E10 is one of the earlier production models and the Pod and headphone In are really malfunctioning, so instead of trying to repair I'm just going to upgrade.
I want a DAC/Amp that's portable and can also drive larger/harder to drive phones so I don't need another unit when I decided to upgrade the Ultrasones. But I don't know what values in the specs relate to how much power a pair of headphones need relative to how much power the Amp gives.
I'd be grateful with any help. Thanks.