Now I use the headphone output of my SF Line 2, but for 2-3 years I used a Headroom Supreme which sounds great. A big advantage of the Supreme is that it is small and built for travel, ie you can get an outboard 4 "C" cell battery box for longer play time, an AC adaptor, and it also has a built in AA battery chamber. Other travel oriented accessories are available.
And it can be plugged into a pre-amp via the tape output terminal either with or without a "splitter". I've used the Supreme with both Senn, 580 and 600s. Cheers. Craig