There's at least a handful of folks using (or who have used) the E7/E9/HD650 combo. Myself included. In my opinion, it works very well, and I like the versatility of a 2-box solution versus a combined DAC/amp unit -- mainly due to connectivity. I've noticed a lot of combined DAC/amp units in this price range don't give you the option of running an analog line in (for amp-only operation), or USB in/analog line-out (for DAC-only operation)... the only choice you get is digital in, amplified analog out. Depending on your situation, this may or may not be important to you. Oh, and I like the sound, too (disclaimer, it's the only dedicated headphone rig I've ever used).