another great thing about the dac1 pre, i cant speak for other dac1 iterations, is the fact that not only does it have two SE HP outputs, it has a balanced out as well if you want to try balanced for the first time, i am aware that technically the XLR out isnt advised to run headphones directly from due to its load characteristics but hell i ran my balanced marlk d5000 straight out of it often and for great duration to compare with my headroom balanced drive and to my ears it was mighty fine! - i think this was because of how well each output is specced and implemented by benchmark and how well it all measures - everythings clean as a whistle!
plus, i have gotten rid of all additional amps and gone back to 'basics' and will be using the dac1 pre hp out as my sole amp now, i should have trusted my ears a long time ago.
also consider lavry and grace units for a warmer less clinical ring to whatever you think you will be pairing it with, but the dac1 holds its value and reputation nicely for resale should it not be your cup of tea!