Of course Kingwa recommended it but I also have a lower priced CD player (Denon DN-C615 and do not want to get rid of it but thought the DSP would be appropriate. Other than that I have no reason except Kingwa recommended it. This is from his site:
Theoretically when using the DSP1, data will be running parallel, achieving near zero jitter state, no matter the level of CD transport attached, be it hypermarket grade or hi-end level, you will still be getting the best and similar sound quality! Practically, through some experiment, although we could perceive the sound quality difference between differently priced and level of CD transports (as an audiophile, you just can’t just follow pure theory, but you must also venture the practical side too), but final result shows that using entry level CD transport or hypermarket grade DVD player, the improvement of sound quality is huge compared to typical digital processor chip like PMD-100, DF1704 etc.