U should get the X7s first! Amps will make more of a difference then DACs. My ultimate advice is save your money and get something really good (600$ budget at least). What comes to mind.
Lyr 3 w/ Multibit module - 699$
Jotunheim w/ Multibit module - 599$
Massdrop x Cavalli Liquid Carbon X - 349$
Massdrop x THX AAA™ 789 Linear Amplifier - 349$ (For both amps, they are in the works making a super balanced DAC to pair with there amps)
Aune S6 - 569$
All those amps to me are pretty much end of the line for any casual listener, u save money by not losing money upgrading slowly and having to sell your old stuff. U got yourself a great headphone but unfortunately it sounds best with better gear and lots of power.
The X7s isn't bad at all its pretty powerful and will do a good job (same specs as the Aune S6), I'm just not so sure about the X1s.