i am stuck between HD 558 and srh 840. I don't mind open or closed design. I just want superior audio quality.
which ones are better and have more dynamics?
By dynamics, I mean the capability of headphones to react quickly to sound changes and the ability to produce quiet and loud sounds.
I'm going to drive the SRH 840 with my E6. Is that enough?
Sometimes (NOT absolutely all the time) one way to tell if an amp will have sufficient dynamic range is to look at the size of the power supply - the transformer, the power capacitors, etc - and on those criteria the E6 is out.
However, of course these can be relative. Aside from whether it might be enough for a given headphone (an iPad has a lot of dynamic range for a good IEM for example), one needs to consider also how loud your listening volume is and how much dynamic range (or how many instruments are playing) your music has to begin with; some might not benefit from a lot more powerful amp. Off the bat though I really wouldn't put much faith on the E6 for that, but don't immediately assume that just about any larger portable or even desktop amp would have a heck of a lot more dynamic range.