The folks at 3dsoundsurge.com could give you the most help. The reason the AE has only three jacks is that each connection caries two channels, the same reason that plugging your headphones into a walkman gives you stereo. 2*3=6 channels of audio. Any 5.1 card will 'decode' Dolby Digital. But this usually only applies to DVDs(as currently, DVDs are the only thing with DD content), so you will still get boring stereo from music and most games. The GTXP may play from all the speakers, but there are only two different CHANNELS playing regardless of how many SPEAKERS are playing. This means that the front left and rear left will be playing the exact same thing at the same time, same with rights. The AE will take a stereo stream (music, games) and 'expand' it into a 5.1 stream(which you can't really call DD, but don't get lost in the terminology). This just means that every speaker is playing something unique at a given point in time, and there is no duplication between the two lefts like on the GTXP. Basically, if you want '3D' sound from your CDs and MP3s, buy a AE. If all you care about is DVDs, both cards will play the exact same thing for them. Games are more complicated, but with the AE you know EVERY game will have 5.1 discrete channels, whereas with the GTXP you may get 4 for some games, maybe just stero for others. Hope this helps.