I know nothing of theBlue Circle unit. However both the Ayre and the Sim were on my short list (along with the Pass X350, Rowland Model 10, and Plinius SA 250Iv). I ended up with the Ayre (which replaced an older Threshold unit). The Ayre definitely seems to have a lower noise floor than the threshold.
However if I had to do it over again there is one mfr I would add to the list: BEL.
However if I had to do it over again there is one mfr I would add to the list: BEL.