Re: Z-5500 or Creative S750?
With digital connection it almost doesn't matter what kind of soundcard you have.
Using for example Prelude will do you nearly no good because none of the high end components will be used and end result will be identical to the cheapest X-Fi.
It all falls down to how good speakers are (and DACs/OPA-AMPs in it). Analog on the other hand is a different beast. Here, everything falls down on both, how good soundcard is and also speakers.
E5200 @ 3,75GHz | 6GB 800MHz DDR2 | ASUS P5Q Deluxe | HD4850 512MB @ 700/2200 | 750-320 HDD | ASUS Xonar Essence STX + Altec Lansing MX5021