It hasn't replaced anything but simply added to the ever increasing number of black boxes I own (although the Onix is arguably the best looking of the bunch). I'm using it in my home office, which is a luxury to say the least. So keep in mind that, as far as I can tell, this one has not been serviced. Or, if it has, it's been awhile. (The numerical code on top of the smoothing caps, for example, is 9404, which may be a date code [April 1994?]). Anyway, overall the thing sounds great. True, the bass is a little soft and mushy. But, overall, it is very involving, lovely presentation, nice PRAT, and so on. It lacks the authority and "slam" of my Naim 202/hicap/250 but the comparison is hardly fair.
To me, it raises the question why, apart from aesthetics, some of us went chasing after a new Onix when Tony Brady (one of the original designers of Onix) is sitting over at Exposure producing equipment that, I suspect, sounds as good or better. Having said that, I have not actually heard any of Tony's Exposure designs but lots of people seem to like what he has been doing.