To be fair, the DT 700 doesn't need an amp, the issue is that it's so good it's picking up on system noise you wouldn't be able to hear on cheap headphones. The noise was always there, the 700 is just letting you know. That's why it needs a DAC, blame your PC :p My last two smartphones had good enough circuitry that I never heard system noise, but my old laptop and modern desktop are very noisy.

This is what I have, and it's been great: www.amazon.com/dp/B07TW2JQNN

But there's cheaper options if you're willing to gamble. No idea if this is actually any good: www.amazon.com/dp/B08L9C7233/