From everything I have heard/read, I am probably looking at the HD650 or the DT880 (or 990) although I wish the Beyers had a removable cord for upgrades and easy replacement from wear. What is interesting, is that the Beyers come in different flavors (32/250/800 ohm) - I wonder which of the 250/600 would be the better match for the DAC-V1?
I've had my DT880 600ohm out just for fun, connected to my UQ the other day, at volume set to 40 out of 100 (this is usually setting for my K240) basically it was not possible to hear what played it was like playing low low volume, guess this version is no match to your V1. I need to crank up high my EAR amp to these 880/600 phones, with my NJC amp things are fine, its made for this stuff and sound stunning.
The cord on the DT880 is just fine, no worries for wasted upgrade" - try if you can get a listen at 250ohm which is reported to be better than 32ohm
DT880 cheaper than HD650..HD600 even better(but not the cord, change neded to HD650 cord) but not suitable unless beefy amp., I'd choose DT770 over 990, (maybe T70 if budget allow) but hearing yourself is basically, some want closed, some want open phones.