I say go with the atom. Here are measurements that compare it to other amps at that price range and above
https://www.audiosciencereview.com/...ents-of-new-jds-labs-atom-headphone-amp.5262/
I would also invest in a $100 dac such as the topping d30 or modi 3. You gain more connectivity options like usb, optical, coax so you can use your headphones on multiple devices (pc, tv, ps4). It will also eliminate possibility of double amping from your desktop and other types of interference. My original set up was a magni 3 connected directly into my pc. I upgraded to magni 3 into smsl sanskrit and heard an improvement. Then magni 3 into topping d30 improved on that. Then replaced the magni 3 with the jds atom and everything came together. Lowering distortion to get the cleanest sound is all that matters, so buying based off measurements is the way to go. i compared my $200 amp/dac stack against more expensive options such as chord mojo, audeze deckard, and ifi black label and couldn't hear a difference.