External Sound Card The gamer seeking enhanced audio performance instead of relying on their PC on-board sound will find excellent value in the GSX 300 external sound card. Paired with a gaming headset, the GSX 300 together with the EPOS Gaming Suite delivers digital sound processing and customizable 7.1 EPOS Surround Sound. An LED ring around the volume dial illuminates blue for 2.0 and red for 7.1 sound mode.