The 5.1 headset I use is the Tritton PC510HDa (MadCatz), an analog connected, 8 driver (one front, rear, center and subwooferspeaker in each earcuff) setup. The soundchip is the Realtek ALC892 with 7.1 and 192kHz/24bit capability, set to 5.1 with no roomtype/equilizer/modulations enabled.
Like stated above, I was able to enjoy full 360° surround in cs:go after tweaking the games speakerposition commands.
I`ve also tried my older Medusa 5.1 ProGamer headset, which is very similar to the Tritton (analog & 8 driver), but the Medusa`s rear- and frontspeakers are physicly in a different aligment inside the earcuffs and therefor dont produce any "deafspots".
I have over 900h in ARMA3, please help me hear full 360° because my current headset is good, but stupid :D