I'm no where near getting into Summit fi, but I've gotten a Audio GD 10es2 and Hm 801 lately, and honestly... I can see how source makes a big differance. Even with my own cans, my w1000x in particular sounds a little thin out of the Audio GD 10Es2, as it's a little to clean [thinking tube for my MODDED w1000x] where as on the other hand my HE 400 and DT 880 sound more open and weighty out of the AGD 10ES2
So it seems the differances in the Dacs [and amps even] make a big differance. I can imagine with more expensive gear it's get even more finnicky. Still I was about to sell my w1000x when I got my hm801... that first day that I plugged into the 801 was a shocker! It REALLY made the w1000x SING. with more clarity and delicacy than my old oDac n mStage combo did.
So if a dac/amp can make a notable differance on mid fi, at ur level it should be equally as important! I should also note my Dt 880 600 ohm, while it was always loud enough out of SE amps... it never really opened up [imo] until I balanced it and drove it with 600/mw the extra power really gave the bass a little more texture and authority, did the same for the low mids, tightend the sound made it a little more tactile. Which for the Dt 880 is an excellent addition!