I've never heard of Cirlinca software, but I don't see any reason why you could'nt be able to discuss it here.
BTW, I do believe that upsampling 16/44 to 24/96 (or beyond) makes an audible difference. I can easily hear a change in the music (for the better IMO) when I convert my music on playback. Normally I don't like to make any conversions and just play all my files at their native formats. But lately I have been playing with upsampling - from both software in MC and in hardware in my DAC's - and I'm liking very much what I am hearing. Like you I've noticed less sibilance on voices. Violins, piano, and acoustic guitar also sound more realistic. A sense of airness, i guess, is what I am hearing around these vocals and instruments. It seems to be more pronounced in the midrange area than anywhere else, but it's definetly there. I also want to say the soundstage appears wider, but this may be the airiness that I'm noticing more than an actual widening of the soundstage.
I have 3 very nice audio systems in my home that I use for primarily music playback. I hear the difference in all 3, but to varying degrees. On my McIntosh pre and amp/Carver Ribbon speaker system I can clearly hear it the most. It is an improvement, no doubt. In my gameroom with my Krell pre/McIntosh amp/B&W speaker system I hear it a bit less than the previous system, but it's still there - an improvement. Lastly, our bedroom system which is a Pioneer reciever and Klipsch speakers it is the least affected by upsampling, though it is still noticable and still an improvement. I believe it is system dependant, and obviously listener dependantand room dependant too. There are a thousand things going against any person when it comes to "hearing" - age, knowledge, cleaness of ear canal, etc., that it's easy for most people to dismiss it, or just not be able to hear it. I'm not one that believes in hype or snake oil. I believe only what I hear. And to my ears, on my system, upsampling is doing a great job at refineing lower resolution material - not adding to it.
Jimmy