Don't expect fireworks. The HD 650 is better than your current choice in every way but they won't shout it at you. Sit back and relax. Your DAC & amp are well up to the job, don't worry about it. Is there a specific genre of music you like?
edit - I meant to say, it's now time to start looking at building a FLAC collection. Your brain will thank you.
I had an experience today that made me question any expectation I secretly harbored about fireworks. Apparently, I fail at discerning between a high quality MP3 and full CD quality; so I am certain I will love my HD-650's because I probably won't be able to tell if they suck. I enjoy a wide variety of music including rock, metal, synth pop, jazz, blues, and classical. Historically, I have been a guitar rock kind of guy, but as my audio equipment grows more capable, my preferences seem to be shifting to the synth pop genre more. Stuff like Depeche Mode. But classic guitar rock jams as much as ever, too. Most of the blues I like (John Lee Hooker, Lightnin' Hopkins) is such bad source recordings that good headphones aren't really going to help much, I think.
There is actually quite a bit of good sounding classic blues. I especially like stereo tracks on Chess from the late 50's -early 60's such as Muddy Waters Folk Singer, Sings Big Bill Broonzy, etc. Also Lightnin Hopkins on Prestige.