I was looking to move up from the Epos ELS-3 and listened to the Onix Ref 1 in a friend's system. I wanted to get away from the slight harshness of the Epos tweeter, especially at low volumes. The Onix was only a marginal improvement, especially surprising given the well respected Vifa tweeter and that my friend was running it with an Onix SP-3. It was better than the Epos, especially at the low end, but not enough better to really impress me.
After some more research and finding a great deal here on Audiogon, I got a pair of VR-1s. Way smoother than the Onix without giving up any detail, even with my old Hafler amp. Bass is slightly better with the VR-1, although the Onix is pretty good there. VR-1 wins hands down on build quality; I have the dark cherry and they're gorgeous plus very solid.
When my wife and I are together listening we do a lot of low level jazz and singer/songwriter stuff, and the detail and soundstaging are terrific. When she's away I crank my prog rock and 80's euro-synth and the VR-1s acquit themselves very well, up the the limits of my Monarchy SM-70 Pro. We're moving soon and if I have a bigger listening room in Oregon I'll buy a second Monarchy. The VR-1s are pretty efficient but can take plenty of juice if you want.
Bottom line, I thought the Onix was good but that the VR-1 is great.