Buy a new headset or a new DAC?

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I have two pairs of the same headphones and I really like them. They are comfortable, sound great and have a microphone. The only problem is they're getting a little old and have both a 1/8" jack for each the headphones and microphone.

At home I have and old Griffin iMic - the old silver one - and it works well. It's probably 15+ years old. At work I have an adapter that takes the two plugs and converts them to one so it works on newer stuff (eg MacBook Pros.) But since the Mac can't control the volume on new monitor's headphone jack, I'm thinking of switching it to a USB adapter as the iMic doesn't have any issues on a hub - the mac can still control it.

My options seem to be:
- New iMic
- Audio Technica ATR2USB https://www.amazon.com/Audio-Technica-AT...op?ie=UTF8
- M-Audio Micro DAC https://www.amazon.com/M-Audio-Micro-DAC...B00X67G4Q8
- New headphones

What say ye?

Here's my current headphones https://www.amazon.com/Plantronics-GameC...B001E45XT4