I wouldnt say its upgraded with respect to sound quality. It does have EAX 5 (Meridian only has EAX 2.0) and uses the Creative X-Fi chip which is very similar to the X-meridian. EAX is environmental audio effects, which for SQ is useless.
Also, the X-meridian has ALL swappable opamps, whereas the X-Fi prelude can only swap the front channel opamp. The other channels are OPA2134's which arent bad, but a superior opamp (LM4562) is used in the front channel of the X-Fi Prelude (which is the ONLY socketed amp on the board). Conversely, the X-meridian can have all opamps swapped to the LM4562

.
The other features DTS, Dolby, Pro logic, etc are not necessarily useful for carpc/car audio. Pure analogue output quality is paramount in car audio. (ie: SNR, RMS output voltage, stereo crosstalk, Dynamic range and ofcourse how the card actually sounds. Imaging, separation of instruments, tonality, clarity,air, timbre, etc).
