After having some real time with my HD650s in the past 2 days, I can say I'm really appreciating their sound again. They sound great with the Amperex tubes. Some details are a bit quieter, but I can still hear everything I used to be able to. It's just not as pronounced. Pretty much the same with my DT880s. I love the punchy bass of the HD650s, and the vocals are just great. They do EDM way better than anyone gives them credit for. They're not the best in class, but they do a great job. The sound isn't as airy and doesn't have as textured bass as some people would prefer, but it's awesome. I'd prefer my DT880s for a lot of songs, but I think I've finally had enough time with them for a while. I'm ready to appreciate the lush HD650s again. I love being able to hear music on multiple kinds of headphones whenever I want, based upon my mental state. It rocks.
+1. This is why I never end up selling my cans... its great having them available in case I happen to be in the mood for that particular sound sig / experience.