Well, I have had my Koss ESP-950's longer, and I still think they do an awesome job. I have had the Stax since about 2005, they were given to me. With the of volume difference problem, I was not thinking I would use them much. So, I tried different amp and, I also ran a heat gun over the lower volume headphone piece. Work like a charm now.
Want to share.
I bought some Stax lambda pro in the past and got with it some user manual and some poster on A3 page for Stax sr-X
because of it I really want to get one, but because the pricing I prefer to keep work with my Lambda pro that I sure that works good as sr-X
I also having the Stax sr-30, that works with no bias voltage, I refoamed the earpads.