How much of a drop in sound quality would there be if I went from my current setup (Little Dot DAC_I -> Schiit Vali -> HD600) to the Momentum over-ear with no DAC or amp, using only either my laptop or Sansa Clip Zip? I am thinking about doing this because I could get back a lot of the money I spent while saving for a better system. Any opinions are appreciated.
Can you drive your HD600 to a confortable level directly out of your Sansa Clip? If you can I honestly doubt the sound differences between direct and the amp\dac stack will be that big. Just tried them directly out of my Galaxy Note 3 and to be honest it sounds just as good as out of my amp to me. That way you can just keep the HD600 if you like their sound.
Ditching the amp stack won't make your HD600 sound like another HP, while the momentum sound very different from the HD600. I have both and I much prefer the HD600.
Again this is assuming you can get them to a volume level you like out of your sources...