Update on amped HD650! And it's a bit iffy on amping. I completely blame my Little Dot MK III. With my HD580 it had a really black background, no humming that I could hear. Now with matched stock 6N6P tubes I can hear a bit of humming at higher volumes. It doesn't switch sides if I switch tubes around. Good news is that I only turn the volume to 10 now instead of 20 like with the HD580. At this level I can't hear it but if I want to crank a favorite song, which happens from time to time, I can start to hear it very faintly. The built in headphone amp of the onboard PC Realtek 892 seems to have a slightly blacker background. Audio quality wise it's a pretty even honestly, which is slightly surprising. The Little Dot MK III has a fun musical tone to it, straight from my computer had a more analytical sound. I don't mean that in a bad way, the tubes just seem to bring emotion to the sound. Everything, bass, mids, and highs, seems smoother, more rounded, or coherent with the each other through the Little Dot. Through the PC it was just all accuracy and not much for the life or feeling that stirs emotions while listening to music. Some songs had great highs but would detract from the mids for example. Honestly I like both types of sound signatures. I just want to get higher quality amps that can present the best of these two worlds. Sometimes you want to hear every tiny note with extreme accuracy and sometimes you want to put on your favorite songs and just loose yourself in the music and forget the world. That's kind of been my findings with most modern solid state vs. vacuum tube amps.
LET THE SHOPPING AND RESEARCH BEGIN!!! (Who am I kidding I've been shopping and researching since before I bought the HD650, haha!)