If you can reach, the SM3 is reputed to be better than the UM3X, it's a little more but it's really one of the best IEM's until you get to customs.
The UM3X IS worth the money, it's just that it nags at you when you know there is other stuff that is more highly acclaimed. I've never heard the SM3 myself though.
I really did like the UM3X, I just had to part with it since it was kind of expensive to keep. The UM2 though, is great, Westone really backs it's products well too and I think they're pretty attractive IEM's.
I sometimes regret not getting the Westone 2 instead, but the UM2 has way lots of bass already and I didn't want to go beyond that.