I’d order a pair of HD6XX in a snap. If worst comes to worst, and customs pick it, even with that extra 50-60€ they will be very worthy still, specially when paired to a P20 balanced all the way.
The timbre (if you’re a bass player will have a taste for that) is one of the most real, engaging and inmmersive I’ve experienced when going balanced from DAC to cans.
First time I was able to easily perceive finger/pick plucking, sliding and notes clearly from electric bass lines.
First time in lots of years also I’ve listened to upright bass on headphones which resembled and felt like on stage… or at least my brain wasn’t shouting “canned sound, canned sound!”.
Magical pairing, and given the price, a no-brainer.
HD6XX aren’t perfect, (slight mid-veil and rolled off treble you quickly get used to) but what counts is the balance in FR, detail, imaging, timbre… and HD6XX overall “package” in this regard is tough to beat.
Making a no-frills balanced cable for the HD6XX is really easy, I offer myself to build you one for free if you’re not into soldering (I’m in Seville). As simple as ordering stock cable, and XLR connector (both available in amazon for around 25€ total), slice the original cable, torch litz strands to burn out the lacquer, solder XLR, and you’re done.