You need another amp to dig out the darkest tightest bass if you love LOUD music. But it´s a very cheap and ok thing to own. With the E11 I´m only using the amp, but that combo is eminent. Can´t understand why, because E11 sucks by itself.
 
Rock on Coke

This is the "Best Buy" I can think of, if you want a combined headset-amp &/or pre-amp for active speakers. I´ve used it with Argon 7460A with really powerful results! As a Head-set amp. it is MUCH better then f.x. Cambridge Audio DacMagic Plus.... It gives the headsets a wonderful warm sound!