Need help whit my headphones impedance

I see you have ATH-m50x in your Equipboard. I bet the m50s are a much better match for the Scarlett. Are you not able to use those headphones instead? If you are currently using the 250 OHM DTs with your Scarlett and they are not loud enough and/or the bass is much weaker than expected, then yes, you need a headphone amp to properly power those higher-impedance headphones. A dedicated headphone amp would connect to the rear line outputs on the Scarlett, not the headphone jack.

Re: whether or not a 80 OHM pair of headphones can be properly driven by the Scarlet, it is my understanding that it's more than just the impedance rating that determines whether or not they would be a good match, but impedance is definitely a big factor. Personally, I would be surprised/disappointed if the Scarlett couldn't drive an 80 OHM pair of headphones well, but I'm not an Engineer, and I don't own a Scarlett. My 64 OHM HD 280s, for example, don't pair as well with some headphone outputs as my ATH-m50s do... the m50s can handle even the crappiest headphone outputs.

(original post edited for brevity)

I have a friend with DTs, I agree they are very nice and very comfortable -- open-back design is great if you have to communicate with others while you work. I know you already know this, but making mixes on headphones that translate well to speakers is very tough -- a headphone amp can compensate for diminshed bass and volume due to very "thirsty" headphones, but mixing on headphones will still be a challenge, even with the amp. Best of Luck!