Something is still better than nothing! I don't know exactly how E6 sounds like but I expect a good quality based on my satisfying experience with E11 and E17. If you insist on upgrading to another sennhaiser headphones HD600 is not a bad choice at all. From 2000 to 2012, people constantly talk about it and many of them really appreciate it. As the old flagship, HD600 won't let you down I believe, though I never had one. And you can just upgrade your amp and DAC later on. The journey of audiophile is not going to be short!