Sennheiser HD600

Well, in that case I am willing to go out an a limb and guess that upgrading to Cardas cables is almost certainly not what you are looking for. I use an older Headroom home headphone amp that I like, but must admit that I haven't compared it to anything else and am not familiar with what you're using. So, apologies, no use when it comes to your actual question. Best of luck.

Maybe not the answer you're looking for, but I found with my 600s that upgrading the headphone cord itself made a shocking difference. Look around the forums, and you'll see quite a bit of raving regarding the Cardas replacement cord for the 600s, which is the one I have. Among all of the various tweaks, wires and various assorted thingamabobs that I've thrown at stereo equipment over the years, the Cardas wire on the Sennheisers was the single best and most transformative decision of the lot -- so much so that I'd hesitate to throw $$ at a new headphone amp before at least giving the Cardas a go. Many a quest for more out of 600s as started and ended just there. Not cheap, but defintely less than $500.... Just a thought.