Daddario PB030 Single String

The great thing about the Daddario range of single strings is that it enables you to fine tune a set of strings, or to build your own custom set if what you want isn't available. They're reasonably priced, so it's feasible to do this. Regarding sound, the strings have a consistent sound, so when you hit the tone you want, you'll be able to replicate it again.
For me, I've used these to make sets up for Tenor guitar until I found exactly what I wanted.