Okay. Then to isolate where the problem lies, the next step would be to compare with another laptop or optical out source. If USB on another laptop sounds about the same as the optical, then your Alienware sounds like it may have something wrong with the optical out (may be just your laptop, may be all of them, I'd look online for reviews that mention the optical out.)
If the USB sounds better than optical on other laptops (the more different laptops you can try the better) then there MIGHT be something wrong with the SPDIF input on your E17. I would see that as a last resort, but if USB sounds better on several different laptops, then that might be the case. The main reason I would doubt this is that the E17 uses the same DAC to decode the digital from either input. This is why USB and optical SHOULD sound much the same. (Laptops really don't generate a high enough quality source to hear the difference between 96k and 192k, like bowie said.)