Microphone for 9 person vocal ensemble

[isngtnr]

I have a 9 person vocal ensemble. We own a Fender Passport Amplification system with 4 mic inputs. Currently the four mics that we use are unidirectional and it doesn't pick up all of the voices well. What kind of microphones should we be using and how many would you recommend for an ensemble of 9 people.
Oliver

[TimmyP1955]

How do they stand when performing?

A row of 9?

A semi-circle of 9?

A row of 5 behind a row of 4?

How far apart are they?

I suspect that one or two coincident pairs would be the way to go.