Like FraGGLeR I didn't notice a significant difference balanced / single ended though there seems to be a slight advantage to running balanced. The caveat is that it's hard to do a back to back comparison, and I haven't be willing to do the work for a blind A/B comparison. I also have little motivation since my HD800 is already balanced for my GS-Xmk2 to it's easier for me to stay balanced.
+1 I have a 4 XLR female to 1/4 adapter which helps me switch when needed which helps. Now I have to figure out if I like my ALO MKIII-B vs the M8. Have not listened extensively but plan to over the weekend.
On another note I guess I got lucky because I got mine new from hifiheavn on ebay and it arrived in two days. Buy it now on Monday and it arrived on Wednesday and have been enjoying them.