One of the reasons I bought my Sennheiser HD25-1 is that it's only 70Ω, which means it can be driven by practically any headphone amp out there and still provide plenty of level if one needs it.
This is a really important thought! Some Headphones have "too much" Ω for some devices. Especially the saffire scarlett is infamous for the weak headphone amp>>> it's not loud enough for a big range of headphones. But the Kempers headphone out should be good enough. It's hot as hell.