Going to play the logical Devil's advocate here and may irk some of you, so here it goes. There is absolutely zero reason that a balanced cable (the 4 pin/pole variety) would improve the quality of sound if under 15'. The whole reason for a balanced cable is to prevent feedback and interference, hence why this type of connection is used in the professional world. Essentially a cable with any current passing through is an antenna, and the greater the length the greater the chance of the signal being distorted by outside sources. Having a balanced cable under 15' will yield zero benefits in a standard application. Any changes you hear are in fact a placebo effect. Sure, there are circumstances that a balanced cable will improve the sound, but ONLY if the environment and/or hardware is abnormal i.e. you live in an old house with crappy 70 year old wiring with the main power line extending off the pole and straight into the breaker (vs being buried underground), or live near a radio tower.
The improvements you folks described is from the material of the wire, not the cable being "balanced"; Technically the pack in cable IS balanced;; Equal length leads feeding both left and right channels. I have a lot of media professionals in my family with decades of experience behind them, and they literally laughed at the idea that a 3' or even 6' cable needs to be 4-pin balanced, let alone improves the sound. It won't, and doesn't. HOWEVER, OCC copper does in fact tighten up the bass, increase focus and separation, and creates an overall smoother, un-inhabited sound. I know this as fact as my ears don't lie. Every headphone in my inventory (sans the Classics) has been re-cabled with OCC copper and I can tell you that that alone improved the sound greater than me re-wiring a single entry to dual. In regards to the 99 Classics, I just got my 3.5mm leads in the mail today, and after I am done typing this post I will be heating up the soldering gun and attaching them bad-boys too an OCC cable. I will post back with my impressions probably tomorrow.
I do have to say though that the Meze balanced cable is not snake oil by any means.
It's cable construction and materials are absolutely stellar! I am not discouraging you fine folks in any way from purchasing it. If you have hardware that has a balanced option, go for it! I would, regardless of the perceived benefits! I just wish Meze offered the same beautiful cable in a standard TRRS option. But please, PLEASE don't assume the improvements in sound is from the cable being fully balanced, rather know that OCC is the real magic maker.
My 2 cents.
P.S. I am on the loaner program for the Sennheiser HDV 820, and WILL be making my own balanced cable that will be interchangeable with all of my cans. My intention is to use a standard balanced OCC cable vs a fully balanced cable, both regular OFC and OCC copper; I will know first hand whether or not to take my foot out of my mouth.