Your questions made me decide to try the GS2Ke on my main system. It uses the PWD MKII as the source running balanced into a RSA Apache with 4 Burson Audio v5S. In fact, its sonics optimized by Ray for my Grado HP2. Definitely a much more resolving and involving system. The GS2Ke scaled really well in this system.
The Apache has a much better single-ended output. The other comparison was between 2 different amps, now it is the same. In this system, while it is still noticeable, it isn't at the level I originally perceived. I would say it is now more in the 5%-7% range.
As noted, the Grado cable is a 12 wire instead of the 8 used on the GH1. I suspect this helps but it makes the cable fatter, otherwise it has very similar physical characteristics.