Choir (esp boys choir) sounds great! Any way to manipulate the tonal values of the voices?

? I'm not sure what you mean, my initial reaction is, there is a way to manipulate the tonal quality of any sound in Montage, it's a synthesizer.

There are choir (vocal) samples of boys choir (indistinguishable from female voices due to formant shape characteristics), mixed voice choirs, there are even several samples of female voices in ensemble. So without knowing what you've heard, what you've explored or exactly what you are looking for, it's hard to supply you with an answer.

Try building your own from the sample sets already on board. Otherwise keep your eyes and ears open for third party libraries that go more in depth - perhaps one or two will land near what you are looking for....