I am a user of K01 too. But I don't think the K01 XLR is a must.
I have the K01 connect both XLR and RCA, XLR with +6DB connected on headphone amp and RCA for speaker amp. The XLR pair are stealth sakra v10. And RCA pair are nordost Odin. I feel that use of XLR for Headphone better only because of the sound stage.
Stupid me, I forgot about the K-01 having a setting which allows either 0dB or +6dB ( XLR only ) , and I've been using +6dB for quite sometime not realising it.
So every time I've compared my XLR's to my RCA's there's been a 6dB difference which is no wonder the XLR's sounded more intense than the RCA's.
It's also made me wonder if there's any difference between silver cable and copper, I say that because I've just compared my interconnects again with the BHSE only, and with the 0dB setting on my source, and I could hear no difference between the two interconnects.
I do hear a difference though between using the 4 pin XLR socket on the GS-X, and the normal headphone socket, because I only use XLR's from my source, and using the 4 pin socket sounds a lot better.