I don't think the sibilance is due to the DAC. What are you using for a digital cable? I do have an Abbas SPDIF cable and you and Steven are welcome to try it. I'm using a Blue Jeans SPDIF and prefer it to the Abbas with the Audial DAC. IMHO, it's very good and inexpensive.Cons:
-Still a little bit of sibilance, no matter which DAC I've listened to, it just doesn't seem to get rid of sibilance, but this one has the least of it that I've heard. This is regardless of it being Redbook, High Res, old or new recordings, although I will say recordings like Muddy Waters: My Captain have less sibilance than something that is new and has been digitally mastered.
I also have an Analysis Plus solo crystal copper digital cable, $290 retail, but my ears like the BJ wire. You guys can try that too.