I read that having a dedicated sound card removes the audio processing load off the CPU and slightly improves performance in games and other applications, is this true?
Should I see perhaps a 3-5 fps increase in battlefield 4?
Would depend on whether your CPU is bottlenecking your system. It is more likely to be your GPU that is holding up your system ... unless your running a GTX 780 with an Athlon XP or something equally imbalanced. Typically discrete sound cards are bought for the sound they produce not performance benefits.