Okay, My understanding is that Bitstream will allow you to decode Multi-channel formats like Dolby Digital 5.1 or DTS 5.1, etc. PCM is uncompressed audio but through two channels only. It is all subjective as far as how does it sound if you only have a 2.1 set up. If that is the case, take a familiar soundtrack or audio track and try it through PCM and then with bitstream. If you can hear the difference, choose the one that sounds the best.