Hi. My first post here. I have the HD595; I had it for a couple of weeks before the E7+E9 combo arrived, three days ago. I am quite dissapointed. Not that it doesn't sound good, it does. But the difference between the HD595 out of my laptop soundcard (Lenovo T61) and USB out/E7/E9 is VERY subtle. So subtle, it's not worth 200$, not for me. The first time I compared I even thought that computer sounds better, but of course this was because it was set to a higher volume. So first thing, I carefully adjusted the volume to get similar levels in both setups. I have to struggle to find a difference; if you listen really hard, it is there. The bass is slightly more precise and SLIGHTLY more powerfull and the overall sound is more ample somehow, but after 5-10 minutes of listening the effect sort of fades out, psychologically I mean. I can't hear any difference in soundstage. I did listen to them comparatively for the last couple of days. I am quite sure I would have a very hard time telling them apart in a blind test (amped vs. non-amped). The headphones are burned in, the amp probably not yet but I don't expect the burn-in to make a huge difference.
Also, they sound just the same with only the E7, without the E9. And you can use the E7's bass boost, which you lose with the combo (unless you give up the docking and connect them via E7's HP out). But I REALLY can't hear any difference between E9+E7 and E7 alone. With the E7 I was able to drive them to maximum volume (60 on the e7) without ANY distortion. The volume is insane, my head started to hurt after about 10 seconds, but there was no distortion at all. So I can't really see (hear) what is the point of E9 with these headphones.
The E7 will make a noticeable difference if you use an iPod as source, particularly due to the bass boost. The iPod just can't output enough bass, so the E7 does make a difference here.
You'll see many people here saying that HD595 will "benefit" from amplification. Maybe they do, but I am afraid I don't find that benefit worth 200$. In my very humble opinion the HD595 are great just on their own. I strongly suggest you hear the difference between amped/unamped before you shell out 200$ of your hard earned cash.
I'll probably open a different thread to discuss this combo and what other options I have in terms of headphones, some that would really "benefit" from an amp like the E9.
