Surround sound was unnecessary. As long as you had stereo headphones you were fine. I had cheap headphones, expensive headphones and even won headphones at LAN events. Directional audio was never an issue on any headset I'd played with.
I tested them all with this video - https://www.youtube.com/watch?v=IUDTlvagjJA
The only headphone issue I had in my decades of playing CS were with open ear headphones (Sennheiser HD555) that reduced the punchiness of bass and made footsteps more difficult to hear in CSS which was a terrible game with terrible audio.
The only headphone issue I had in my decades of playing CS were with open ear headphones (Sennheiser HD555) that reduced the punchiness of bass and made footsteps more difficult to hear in CSS which was a terrible game with terrible audio.