Ty knows WAY more than I could ever even imagine about audio, but I'm starting to get into the realm of audio recording and am about to invest in microphones for a similar purpose. Since I started filming some local school concerts, I have decided to upgrade my audio kit from a Sony PCM-d50 up to real microphones hooked up to a mixer by my cameras. I thought I would share what I'm looking into for recording band, orchestra, and choral concerts in an auditorium.
The Oktava MC012 microphone has gotten some good reviews as a powerful performer. I'm looking into getting a stereo pair of MC012s and mounting them on top of a Manfrotto 004BAC light stand. Some extra height in a stand might be nice, but 13' seems like it will be good enough to start with and it won't break the bank.
Anyway, I hope that might help you a little in your endeavor! Best of luck to you.