I don't have a UX anything, but I've got several SM57 and SM7b - the SM7b is lower output than the SM57, btw.
What I'm about to say is a little contrary to the predominant wisdom, but I submit this - you don't need a preamp with a lot of gain for the SM7b - rather, you need 1) a clean preamp - one that doesn't add much noise to the signal, even if its overall gain isn't that much; and 2) a method for live monitoring that will allow a player to hear the signal in headphones while tracking, if that's a concern.
The reason I say this is that, with the UX2, you're certainly recording to a computer - if you have a track that you recorded with the SM7b that is too quiet, you simply boost the gain inside the computer to get it up to the level you want. If your preamp was *quiet*, you won't have a problem doing this, and, I maintain, the result will be pretty much the same as if you had used a quiet preamp with a lot of gain in the first place. If your preamp is *noisy*, it won't really matter how much gain it has, because the lower signal of the SM7b will not figure favorably into the signal-to-noise ratio, and it won't matter whether you turn it up at the preamp stage or the computer stage - the noise will be there.
The only other practical problem that us home-reckers face is that we want to wear headphones while we track, and hear both a click track and/or drums / other instruments, along with the sound of what we're playing/singing - this is an issue with any set up, and it's a bad idea to track too hot merely so that you can hear yourself playing in any event - with the SM7b, it's more pronounced - you need to make sure you have a way to amplify the signal in the computer or afterward while tracking to address the issue.
If the UX2 satisfies both these conditions - it's quiet and it provides a way for you to get a good headphone monitoring level (or you have another way to do that), then you should be good.
