Audio 4 sound card is a 2 channel unit and the Audio 8 is a 4 channel. Really comes down to how many channels you will be using. Pretty sure they preform the same, the only difference is how many channels they have. In saying that, if you only need 2 channels I would still probably go for the Audio 8, you may never know when your circumstances change and you need 3-4 channels. If you get the Audio 8 now it will save the drama of updating later on down the track if need be.