Back in the 70's and '80s, headphones were considered accessories. Quite a few audio stores didn't carry headphones at all, but if they did it was probably the Sennheiser HE414's with the yellow foam pads. I think the Koss Pro 4AAA was another big seller then, and Koss also had some early electrostatics like the ESP6. I have no idea how common it was for audio stores to carry Stax back then but probably not many did. The big mags were High Fidelity and Stereo Review. Stereophile had been around since the 1960's, and The Absolute Sound started in the mid 1970's but they were relatively low circulation. I found out about Stax from Stereophile, and I bought my Stax SR-5/SRD-6 used at a Q Audio, little shop in Cambridge, MA which specialized in selling used gear, without auditioning them, mainly because my speakers were also electrostatic - the original Quad ESLs.