Pros: Great Looking, Clear Sound
I recently purchased an Exo Series cable from Plussound for my HD650s. I chose the silver/gold 26/50 wire and a Rhodium straight 1/8" plug. Now that the cable has burned in, I can hear a definite increase in detail and clarity compared to the stock cable. It matches up very well with the Sennheiser's and helps bring them a bit more alive. No more Sennheiser veil, at least to my ears. I like the sound of my HD650s with this cable better than the sound of the much more expensive Beyerdynamic T1s I am trying out. So this aftermarket cable will actually end up saving me a lot of money!
In addition, I found Christian at Plussound to be incredibly patient, helpful and flexible before and after the sale. It is a treat to find a company that offers such great customer service.