And thats where you are wrong my friend.
DNSe accentuates the hissing. Hissing is always present, no matter what firmware version your using. But the known fact is that DNSe's PCE makes the noise worse. Turning it off doesnt perform any miracles, it just makes the hissing less present.
However, if you are using a decent set of phones' you'll get annoyed anyhow.