I did spend about an hour, after you first posted, switching back and forth between Clou and stock. The immediate observations from that exercise were that the Clou has deeper bass extension (the obvious); the Clou is more revealing (I can hear more of what is in a recording); the Clou is slightly more detailed. People mentioned greater overall transparency through the Clou, and I'm not sure I hear that. We'll see...
But as I sit here now, listening through the stock cable, I won't say I dislike it. But I do miss what get through the Clou. And I just can't hear that midrange film or mask that you say the muddy Clou bass generates. I am just sitting here hearing less bass (not tighter bass), less music, and less detail. If anything, the sound through the *stock* cable sounds a tad muffled or less dynamic.
One thing for sure, however, is this... Changing tubes in my MG Head DT has a far greater effect on the sound than changing the cables. In terms of bang for the buck, there is no comparison.
That's what I hear, but I'll give it the rest of the day. And, trust me, the $100 or so I spent on the Clou isn't biasing me. I'd give it up in a second in the name of better sound - I wear these things 10+ hours a day!
Have a good one.
Brian.