Thanks for everyone's suggestions. I've done just aobut everything I can with the current equipment I have on hand to try to hear the subtle differences between the dithers and wordlengths. Even thought the differences were obvious in another system I have listened to in the past, I just have to accept the fact that I won't hear the differences on mine.
I believe my DAC might be the culprit since Meridian recommends one using a DAC with at least 18 bits, and my sigma has only 1bit (with 18bit resolution).
I have hooked my preamp back up, and used the 518 in type 1 mode with no attenuation, this means no loss of bits, yet I still cannot hear any sonic difference/improvements by playing around with the dsps.
However, the 518 allows me to hook the dac straight into the amp and dejitters the jitters. This, by itself, has made me a happy happy camper.
I will try to listen for the dithers after I upgrade my digital fronts, which won't be in the near future unless I see a Sonic Frontiers SFD1 DAC for about.. 400?