Just to be clear guys. Evaluating dacs comes more easily after you get used to a few nice quality dacs. Once you know what to look for and where it really doesn't take that long to hear a difference. Like 10 seconds of a passage of song that is super complex with lots of things happening will literally reveal almost everything about that dac. A lesser dac will smear the details and the attacks will sound blunted and messy at the end or the tonality will be off, bloated or recessed somewhere. There is also resolution, the ability to extract micro-details. etc. I mean seriously once you hear the difference it's startling and hard to go back to $100 dacs. The reason it takes so long to figure out the difference initally is just a lack of experience. Once you have the experience the differences are very in your face hard to miss even after just a few second of listening. It doesn't take weeks or months everytime you get a new dac. I'm just saying your very first one might take that long.
And no need to jump into $10k territory. Just try the $600 Concero, or if you can swing a get a X-Sabre, DA8, Anedio D2. Or buy any of these used if you want them cheaper. They're all near $1000 or under. You can probably resell them at the exact price you bought them for. People spend $1000 on headphones all the time, LCD-2/T1/HD800, hell even the HD700 went for a $1000. Try a dac in that range if you already have a phone of this caliber and get ready to smile big and eat crow.
Ahhh, that felt good.