Audio System: Windows® compatible sound card (*Sound Blaster® Audigy(tm) series sound card RECOMMENDED) (NVIDIA® nForce or other motherboards/soundcards containing the Dolby® Digital Interactive Content Encoder required for Dolby Digital audio. Also RECOMMENDED) This was taken form the system requirements. When it says that you need "Interactive content Encoder" Does that mean you need a external amp/chip. Or just some software codec???