JMT, as is always the case with cables, each one involves a different set of trade offs.
The Kimber cable is very smooth and detailed, but like the interconnect it can also sound a bit thin and wiry, as well as losing a bit of deep bass.
The DiMarzio cable is full-bodied, with good bass, but it is too dark and coloured for my tastes, and has rolled-off highs.
The Grado cable is slightly grainier than the Kimber or DiMarzio cables, without the liquid smoothness which the other two have. However, it leaves the tonal balance more-or-less intact, which is what I personally prefer in an extension cable.
I haven't heard the "Teds Excellent" (not sure what that is) so I can't comment on that one.
There are also the Sonic Horizons extensions, of which there have been a few good reports.
I am hoping that Headroom will solve this problem by providing either a Clou cable extension, or a 6m version of the Clou sennheiser cable.
All of the extension cables make an audible difference, so it is a question of finding one you can live with. The alternative is to use longer interconnects to get your headphone amp closer to your listening position, which is far preferable.
