I am not expert at all in dac...
but if i was upgrading my basic one , which satisfy me completely, i will pick a Choueri BACCH dac...Before throwing money, check his credentials and his realization... In case... I must admit that this is the only upgrade i will ever need...I like my actual system without being able to fault it...So imperfect it is , nothing is perfect at any price, i did not detect any fault in my actua headphone system.It is after my dedicated/room now lost, the best i listened to in my life , Stax included...
Why Choueri dac then ?
it is not just a dac...
It is a " virtual room systems" for speakers and headphone with ears measurements ... It is a patented system of filters which introduce no timbre degradation and made headphone as speakers out of the head... And it make speakers working WITHOUT the room acoustic problem at all...And trust me on this, the room acoustic is the most important problem in audio with speakers and not the dac, save if the one you own is bad...
i am lucky because my headphone is one of the rare one already speaker-like but it will be way more externalized in the room with Dr Choueri dac ... I never listened to it, no... but i read all there is and it is enough to want it... Choueri is a top physicist and a top acoustician..
Apart from this dac i will never need anything... I dont even need anything without it right now 😎😊 I am not only lucky , i work a lot to create my 2 systems... ... read about Choueri in case...For a reason i dont understand this dac/ virtual room system is not well known...It kill any other dac because no other dac suppress all acoustic room problem with no timbre degradation..
https://www.theabsolutesound.com/articles/theoretica-applied-physics-bacch-sp-adio-stereo-purifier/
The only problem for me is that my 700 bucks system satisfy me completely, because my amp is top and my headphone over the top... 😊 The BACCH filters in hardware dac will cost 15,000 bucks ... Less expansive if we use a laptop as source and hardware for the Filters set... Anyway as i said it is the only possible upgrade for me...