Just use them with the dongle you have and enjoy your purchase once it arrives. Let amps, dacs, tubes and whatnot for what it is right now and just enjoy some high res recordings instead. Once you have the idea that you're "getting used" to the sound signature of your set off cans and dongle then it's time to stir it up a bit and buy something like a dac/amp combo or maybe a pair of closed back to listen to occasionally next to your open back headphones. But for now, just enjoy your set of cans and don't get too caught up in chasing the dragon;)