You don't need a DAC unless want to bypass the one in the device you're playing music on (tablet, cellphone, computer). As for an amp, that is subjective. It depends on your source, how loud you want to be able to listen and how much you care about sound quality. These are half the impedance of the HD600 so they're easier to drive. I can get good volume directly from an iPod Shuffle but the sound quality is somewhat compromised but still quite good. They sound great directly from the headphone jack on my CD player but sound even better through a good headphone amp as expected. For me, I can use these happily without a separate headphone amp but since I have some decent headphone amps (TEAC HA-501 & JDS Atom), I use them when I want just a little more.